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   1  //     Underscore.js 1.8.3
   2  //     http://underscorejs.org
   3  //     (c) 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
   4  //     Underscore may be freely distributed under the MIT license.
   5  
   6  (function() {
   7  
   8    // Baseline setup
   9    // --------------
  10  
  11    // Establish the root object, `window` in the browser, or `exports` on the server.
  12    var root = this;
  13  
  14    // Save the previous value of the `_` variable.
  15    var previousUnderscore = root._;
  16  
  17    // Save bytes in the minified (but not gzipped) version:
  18    var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
  19  
  20    // Create quick reference variables for speed access to core prototypes.
  21    var
  22      push             = ArrayProto.push,
  23      slice            = ArrayProto.slice,
  24      toString         = ObjProto.toString,
  25      hasOwnProperty   = ObjProto.hasOwnProperty;
  26  
  27    // All **ECMAScript 5** native function implementations that we hope to use
  28    // are declared here.
  29    var
  30      nativeIsArray      = Array.isArray,
  31      nativeKeys         = Object.keys,
  32      nativeBind         = FuncProto.bind,
  33      nativeCreate       = Object.create;
  34  
  35    // Naked function reference for surrogate-prototype-swapping.
  36    var Ctor = function(){};
  37  
  38    // Create a safe reference to the Underscore object for use below.
  39    var _ = function(obj) {
  40      if (obj instanceof _) return obj;
  41      if (!(this instanceof _)) return new _(obj);
  42      this._wrapped = obj;
  43    };
  44  
  45    // Export the Underscore object for **Node.js**, with
  46    // backwards-compatibility for the old `require()` API. If we're in
  47    // the browser, add `_` as a global object.
  48    if (typeof exports !== 'undefined') {
  49      if (typeof module !== 'undefined' && module.exports) {
  50        exports = module.exports = _;
  51      }
  52      exports._ = _;
  53    } else {
  54      root._ = _;
  55    }
  56  
  57    // Current version.
  58    _.VERSION = '1.8.3';
  59  
  60    // Internal function that returns an efficient (for current engines) version
  61    // of the passed-in callback, to be repeatedly applied in other Underscore
  62    // functions.
  63    var optimizeCb = function(func, context, argCount) {
  64      if (context === void 0) return func;
  65      switch (argCount == null ? 3 : argCount) {
  66        case 1: return function(value) {
  67          return func.call(context, value);
  68        };
  69        case 2: return function(value, other) {
  70          return func.call(context, value, other);
  71        };
  72        case 3: return function(value, index, collection) {
  73          return func.call(context, value, index, collection);
  74        };
  75        case 4: return function(accumulator, value, index, collection) {
  76          return func.call(context, accumulator, value, index, collection);
  77        };
  78      }
  79      return function() {
  80        return func.apply(context, arguments);
  81      };
  82    };
  83  
  84    // A mostly-internal function to generate callbacks that can be applied
  85    // to each element in a collection, returning the desired result — either
  86    // identity, an arbitrary callback, a property matcher, or a property accessor.
  87    var cb = function(value, context, argCount) {
  88      if (value == null) return _.identity;
  89      if (_.isFunction(value)) return optimizeCb(value, context, argCount);
  90      if (_.isObject(value)) return _.matcher(value);
  91      return _.property(value);
  92    };
  93    _.iteratee = function(value, context) {
  94      return cb(value, context, Infinity);
  95    };
  96  
  97    // An internal function for creating assigner functions.
  98    var createAssigner = function(keysFunc, undefinedOnly) {
  99      return function(obj) {
 100        var length = arguments.length;
 101        if (length < 2 || obj == null) return obj;
 102        for (var index = 1; index < length; index++) {
 103          var source = arguments[index],
 104              keys = keysFunc(source),
 105              l = keys.length;
 106          for (var i = 0; i < l; i++) {
 107            var key = keys[i];
 108            if (!undefinedOnly || obj[key] === void 0) obj[key] = source[key];
 109          }
 110        }
 111        return obj;
 112      };
 113    };
 114  
 115    // An internal function for creating a new object that inherits from another.
 116    var baseCreate = function(prototype) {
 117      if (!_.isObject(prototype)) return {};
 118      if (nativeCreate) return nativeCreate(prototype);
 119      Ctor.prototype = prototype;
 120      var result = new Ctor;
 121      Ctor.prototype = null;
 122      return result;
 123    };
 124  
 125    var property = function(key) {
 126      return function(obj) {
 127        return obj == null ? void 0 : obj[key];
 128      };
 129    };
 130  
 131    // Helper for collection methods to determine whether a collection
 132    // should be iterated as an array or as an object
 133    // Related: http://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength
 134    // Avoids a very nasty iOS 8 JIT bug on ARM-64. #2094
 135    var MAX_ARRAY_INDEX = Math.pow(2, 53) - 1;
 136    var getLength = property('length');
 137    var isArrayLike = function(collection) {
 138      var length = getLength(collection);
 139      return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
 140    };
 141  
 142    // Collection Functions
 143    // --------------------
 144  
 145    // The cornerstone, an `each` implementation, aka `forEach`.
 146    // Handles raw objects in addition to array-likes. Treats all
 147    // sparse array-likes as if they were dense.
 148    _.each = _.forEach = function(obj, iteratee, context) {
 149      iteratee = optimizeCb(iteratee, context);
 150      var i, length;
 151      if (isArrayLike(obj)) {
 152        for (i = 0, length = obj.length; i < length; i++) {
 153          iteratee(obj[i], i, obj);
 154        }
 155      } else {
 156        var keys = _.keys(obj);
 157        for (i = 0, length = keys.length; i < length; i++) {
 158          iteratee(obj[keys[i]], keys[i], obj);
 159        }
 160      }
 161      return obj;
 162    };
 163  
 164    // Return the results of applying the iteratee to each element.
 165    _.map = _.collect = function(obj, iteratee, context) {
 166      iteratee = cb(iteratee, context);
 167      var keys = !isArrayLike(obj) && _.keys(obj),
 168          length = (keys || obj).length,
 169          results = Array(length);
 170      for (var index = 0; index < length; index++) {
 171        var currentKey = keys ? keys[index] : index;
 172        results[index] = iteratee(obj[currentKey], currentKey, obj);
 173      }
 174      return results;
 175    };
 176  
 177    // Create a reducing function iterating left or right.
 178    function createReduce(dir) {
 179      // Optimized iterator function as using arguments.length
 180      // in the main function will deoptimize the, see #1991.
 181      function iterator(obj, iteratee, memo, keys, index, length) {
 182        for (; index >= 0 && index < length; index += dir) {
 183          var currentKey = keys ? keys[index] : index;
 184          memo = iteratee(memo, obj[currentKey], currentKey, obj);
 185        }
 186        return memo;
 187      }
 188  
 189      return function(obj, iteratee, memo, context) {
 190        iteratee = optimizeCb(iteratee, context, 4);
 191        var keys = !isArrayLike(obj) && _.keys(obj),
 192            length = (keys || obj).length,
 193            index = dir > 0 ? 0 : length - 1;
 194        // Determine the initial value if none is provided.
 195        if (arguments.length < 3) {
 196          memo = obj[keys ? keys[index] : index];
 197          index += dir;
 198        }
 199        return iterator(obj, iteratee, memo, keys, index, length);
 200      };
 201    }
 202  
 203    // **Reduce** builds up a single result from a list of values, aka `inject`,
 204    // or `foldl`.
 205    _.reduce = _.foldl = _.inject = createReduce(1);
 206  
 207    // The right-associative version of reduce, also known as `foldr`.
 208    _.reduceRight = _.foldr = createReduce(-1);
 209  
 210    // Return the first value which passes a truth test. Aliased as `detect`.
 211    _.find = _.detect = function(obj, predicate, context) {
 212      var key;
 213      if (isArrayLike(obj)) {
 214        key = _.findIndex(obj, predicate, context);
 215      } else {
 216        key = _.findKey(obj, predicate, context);
 217      }
 218      if (key !== void 0 && key !== -1) return obj[key];
 219    };
 220  
 221    // Return all the elements that pass a truth test.
 222    // Aliased as `select`.
 223    _.filter = _.select = function(obj, predicate, context) {
 224      var results = [];
 225      predicate = cb(predicate, context);
 226      _.each(obj, function(value, index, list) {
 227        if (predicate(value, index, list)) results.push(value);
 228      });
 229      return results;
 230    };
 231  
 232    // Return all the elements for which a truth test fails.
 233    _.reject = function(obj, predicate, context) {
 234      return _.filter(obj, _.negate(cb(predicate)), context);
 235    };
 236  
 237    // Determine whether all of the elements match a truth test.
 238    // Aliased as `all`.
 239    _.every = _.all = function(obj, predicate, context) {
 240      predicate = cb(predicate, context);
 241      var keys = !isArrayLike(obj) && _.keys(obj),
 242          length = (keys || obj).length;
 243      for (var index = 0; index < length; index++) {
 244        var currentKey = keys ? keys[index] : index;
 245        if (!predicate(obj[currentKey], currentKey, obj)) return false;
 246      }
 247      return true;
 248    };
 249  
 250    // Determine if at least one element in the object matches a truth test.
 251    // Aliased as `any`.
 252    _.some = _.any = function(obj, predicate, context) {
 253      predicate = cb(predicate, context);
 254      var keys = !isArrayLike(obj) && _.keys(obj),
 255          length = (keys || obj).length;
 256      for (var index = 0; index < length; index++) {
 257        var currentKey = keys ? keys[index] : index;
 258        if (predicate(obj[currentKey], currentKey, obj)) return true;
 259      }
 260      return false;
 261    };
 262  
 263    // Determine if the array or object contains a given item (using `===`).
 264    // Aliased as `includes` and `include`.
 265    _.contains = _.includes = _.include = function(obj, item, fromIndex, guard) {
 266      if (!isArrayLike(obj)) obj = _.values(obj);
 267      if (typeof fromIndex != 'number' || guard) fromIndex = 0;
 268      return _.indexOf(obj, item, fromIndex) >= 0;
 269    };
 270  
 271    // Invoke a method (with arguments) on every item in a collection.
 272    _.invoke = function(obj, method) {
 273      var args = slice.call(arguments, 2);
 274      var isFunc = _.isFunction(method);
 275      return _.map(obj, function(value) {
 276        var func = isFunc ? method : value[method];
 277        return func == null ? func : func.apply(value, args);
 278      });
 279    };
 280  
 281    // Convenience version of a common use case of `map`: fetching a property.
 282    _.pluck = function(obj, key) {
 283      return _.map(obj, _.property(key));
 284    };
 285  
 286    // Convenience version of a common use case of `filter`: selecting only objects
 287    // containing specific `key:value` pairs.
 288    _.where = function(obj, attrs) {
 289      return _.filter(obj, _.matcher(attrs));
 290    };
 291  
 292    // Convenience version of a common use case of `find`: getting the first object
 293    // containing specific `key:value` pairs.
 294    _.findWhere = function(obj, attrs) {
 295      return _.find(obj, _.matcher(attrs));
 296    };
 297  
 298    // Return the maximum element (or element-based computation).
 299    _.max = function(obj, iteratee, context) {
 300      var result = -Infinity, lastComputed = -Infinity,
 301          value, computed;
 302      if (iteratee == null && obj != null) {
 303        obj = isArrayLike(obj) ? obj : _.values(obj);
 304        for (var i = 0, length = obj.length; i < length; i++) {
 305          value = obj[i];
 306          if (value > result) {
 307            result = value;
 308          }
 309        }
 310      } else {
 311        iteratee = cb(iteratee, context);
 312        _.each(obj, function(value, index, list) {
 313          computed = iteratee(value, index, list);
 314          if (computed > lastComputed || computed === -Infinity && result === -Infinity) {
 315            result = value;
 316            lastComputed = computed;
 317          }
 318        });
 319      }
 320      return result;
 321    };
 322  
 323    // Return the minimum element (or element-based computation).
 324    _.min = function(obj, iteratee, context) {
 325      var result = Infinity, lastComputed = Infinity,
 326          value, computed;
 327      if (iteratee == null && obj != null) {
 328        obj = isArrayLike(obj) ? obj : _.values(obj);
 329        for (var i = 0, length = obj.length; i < length; i++) {
 330          value = obj[i];
 331          if (value < result) {
 332            result = value;
 333          }
 334        }
 335      } else {
 336        iteratee = cb(iteratee, context);
 337        _.each(obj, function(value, index, list) {
 338          computed = iteratee(value, index, list);
 339          if (computed < lastComputed || computed === Infinity && result === Infinity) {
 340            result = value;
 341            lastComputed = computed;
 342          }
 343        });
 344      }
 345      return result;
 346    };
 347  
 348    // Shuffle a collection, using the modern version of the
 349    // [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
 350    _.shuffle = function(obj) {
 351      var set = isArrayLike(obj) ? obj : _.values(obj);
 352      var length = set.length;
 353      var shuffled = Array(length);
 354      for (var index = 0, rand; index < length; index++) {
 355        rand = _.random(0, index);
 356        if (rand !== index) shuffled[index] = shuffled[rand];
 357        shuffled[rand] = set[index];
 358      }
 359      return shuffled;
 360    };
 361  
 362    // Sample **n** random values from a collection.
 363    // If **n** is not specified, returns a single random element.
 364    // The internal `guard` argument allows it to work with `map`.
 365    _.sample = function(obj, n, guard) {
 366      if (n == null || guard) {
 367        if (!isArrayLike(obj)) obj = _.values(obj);
 368        return obj[_.random(obj.length - 1)];
 369      }
 370      return _.shuffle(obj).slice(0, Math.max(0, n));
 371    };
 372  
 373    // Sort the object's values by a criterion produced by an iteratee.
 374    _.sortBy = function(obj, iteratee, context) {
 375      iteratee = cb(iteratee, context);
 376      return _.pluck(_.map(obj, function(value, index, list) {
 377        return {
 378          value: value,
 379          index: index,
 380          criteria: iteratee(value, index, list)
 381        };
 382      }).sort(function(left, right) {
 383        var a = left.criteria;
 384        var b = right.criteria;
 385        if (a !== b) {
 386          if (a > b || a === void 0) return 1;
 387          if (a < b || b === void 0) return -1;
 388        }
 389        return left.index - right.index;
 390      }), 'value');
 391    };
 392  
 393    // An internal function used for aggregate "group by" operations.
 394    var group = function(behavior) {
 395      return function(obj, iteratee, context) {
 396        var result = {};
 397        iteratee = cb(iteratee, context);
 398        _.each(obj, function(value, index) {
 399          var key = iteratee(value, index, obj);
 400          behavior(result, value, key);
 401        });
 402        return result;
 403      };
 404    };
 405  
 406    // Groups the object's values by a criterion. Pass either a string attribute
 407    // to group by, or a function that returns the criterion.
 408    _.groupBy = group(function(result, value, key) {
 409      if (_.has(result, key)) result[key].push(value); else result[key] = [value];
 410    });
 411  
 412    // Indexes the object's values by a criterion, similar to `groupBy`, but for
 413    // when you know that your index values will be unique.
 414    _.indexBy = group(function(result, value, key) {
 415      result[key] = value;
 416    });
 417  
 418    // Counts instances of an object that group by a certain criterion. Pass
 419    // either a string attribute to count by, or a function that returns the
 420    // criterion.
 421    _.countBy = group(function(result, value, key) {
 422      if (_.has(result, key)) result[key]++; else result[key] = 1;
 423    });
 424  
 425    // Safely create a real, live array from anything iterable.
 426    _.toArray = function(obj) {
 427      if (!obj) return [];
 428      if (_.isArray(obj)) return slice.call(obj);
 429      if (isArrayLike(obj)) return _.map(obj, _.identity);
 430      return _.values(obj);
 431    };
 432  
 433    // Return the number of elements in an object.
 434    _.size = function(obj) {
 435      if (obj == null) return 0;
 436      return isArrayLike(obj) ? obj.length : _.keys(obj).length;
 437    };
 438  
 439    // Split a collection into two arrays: one whose elements all satisfy the given
 440    // predicate, and one whose elements all do not satisfy the predicate.
 441    _.partition = function(obj, predicate, context) {
 442      predicate = cb(predicate, context);
 443      var pass = [], fail = [];
 444      _.each(obj, function(value, key, obj) {
 445        (predicate(value, key, obj) ? pass : fail).push(value);
 446      });
 447      return [pass, fail];
 448    };
 449  
 450    // Array Functions
 451    // ---------------
 452  
 453    // Get the first element of an array. Passing **n** will return the first N
 454    // values in the array. Aliased as `head` and `take`. The **guard** check
 455    // allows it to work with `_.map`.
 456    _.first = _.head = _.take = function(array, n, guard) {
 457      if (array == null) return void 0;
 458      if (n == null || guard) return array[0];
 459      return _.initial(array, array.length - n);
 460    };
 461  
 462    // Returns everything but the last entry of the array. Especially useful on
 463    // the arguments object. Passing **n** will return all the values in
 464    // the array, excluding the last N.
 465    _.initial = function(array, n, guard) {
 466      return slice.call(array, 0, Math.max(0, array.length - (n == null || guard ? 1 : n)));
 467    };
 468  
 469    // Get the last element of an array. Passing **n** will return the last N
 470    // values in the array.
 471    _.last = function(array, n, guard) {
 472      if (array == null) return void 0;
 473      if (n == null || guard) return array[array.length - 1];
 474      return _.rest(array, Math.max(0, array.length - n));
 475    };
 476  
 477    // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
 478    // Especially useful on the arguments object. Passing an **n** will return
 479    // the rest N values in the array.
 480    _.rest = _.tail = _.drop = function(array, n, guard) {
 481      return slice.call(array, n == null || guard ? 1 : n);
 482    };
 483  
 484    // Trim out all falsy values from an array.
 485    _.compact = function(array) {
 486      return _.filter(array, _.identity);
 487    };
 488  
 489    // Internal implementation of a recursive `flatten` function.
 490    var flatten = function(input, shallow, strict, startIndex) {
 491      var output = [], idx = 0;
 492      for (var i = startIndex || 0, length = getLength(input); i < length; i++) {
 493        var value = input[i];
 494        if (isArrayLike(value) && (_.isArray(value) || _.isArguments(value))) {
 495          //flatten current level of array or arguments object
 496          if (!shallow) value = flatten(value, shallow, strict);
 497          var j = 0, len = value.length;
 498          output.length += len;
 499          while (j < len) {
 500            output[idx++] = value[j++];
 501          }
 502        } else if (!strict) {
 503          output[idx++] = value;
 504        }
 505      }
 506      return output;
 507    };
 508  
 509    // Flatten out an array, either recursively (by default), or just one level.
 510    _.flatten = function(array, shallow) {
 511      return flatten(array, shallow, false);
 512    };
 513  
 514    // Return a version of the array that does not contain the specified value(s).
 515    _.without = function(array) {
 516      return _.difference(array, slice.call(arguments, 1));
 517    };
 518  
 519    // Produce a duplicate-free version of the array. If the array has already
 520    // been sorted, you have the option of using a faster algorithm.
 521    // Aliased as `unique`.
 522    _.uniq = _.unique = function(array, isSorted, iteratee, context) {
 523      if (!_.isBoolean(isSorted)) {
 524        context = iteratee;
 525        iteratee = isSorted;
 526        isSorted = false;
 527      }
 528      if (iteratee != null) iteratee = cb(iteratee, context);
 529      var result = [];
 530      var seen = [];
 531      for (var i = 0, length = getLength(array); i < length; i++) {
 532        var value = array[i],
 533            computed = iteratee ? iteratee(value, i, array) : value;
 534        if (isSorted) {
 535          if (!i || seen !== computed) result.push(value);
 536          seen = computed;
 537        } else if (iteratee) {
 538          if (!_.contains(seen, computed)) {
 539            seen.push(computed);
 540            result.push(value);
 541          }
 542        } else if (!_.contains(result, value)) {
 543          result.push(value);
 544        }
 545      }
 546      return result;
 547    };
 548  
 549    // Produce an array that contains the union: each distinct element from all of
 550    // the passed-in arrays.
 551    _.union = function() {
 552      return _.uniq(flatten(arguments, true, true));
 553    };
 554  
 555    // Produce an array that contains every item shared between all the
 556    // passed-in arrays.
 557    _.intersection = function(array) {
 558      var result = [];
 559      var argsLength = arguments.length;
 560      for (var i = 0, length = getLength(array); i < length; i++) {
 561        var item = array[i];
 562        if (_.contains(result, item)) continue;
 563        for (var j = 1; j < argsLength; j++) {
 564          if (!_.contains(arguments[j], item)) break;
 565        }
 566        if (j === argsLength) result.push(item);
 567      }
 568      return result;
 569    };
 570  
 571    // Take the difference between one array and a number of other arrays.
 572    // Only the elements present in just the first array will remain.
 573    _.difference = function(array) {
 574      var rest = flatten(arguments, true, true, 1);
 575      return _.filter(array, function(value){
 576        return !_.contains(rest, value);
 577      });
 578    };
 579  
 580    // Zip together multiple lists into a single array -- elements that share
 581    // an index go together.
 582    _.zip = function() {
 583      return _.unzip(arguments);
 584    };
 585  
 586    // Complement of _.zip. Unzip accepts an array of arrays and groups
 587    // each array's elements on shared indices
 588    _.unzip = function(array) {
 589      var length = array && _.max(array, getLength).length || 0;
 590      var result = Array(length);
 591  
 592      for (var index = 0; index < length; index++) {
 593        result[index] = _.pluck(array, index);
 594      }
 595      return result;
 596    };
 597  
 598    // Converts lists into objects. Pass either a single array of `[key, value]`
 599    // pairs, or two parallel arrays of the same length -- one of keys, and one of
 600    // the corresponding values.
 601    _.object = function(list, values) {
 602      var result = {};
 603      for (var i = 0, length = getLength(list); i < length; i++) {
 604        if (values) {
 605          result[list[i]] = values[i];
 606        } else {
 607          result[list[i][0]] = list[i][1];
 608        }
 609      }
 610      return result;
 611    };
 612  
 613    // Generator function to create the findIndex and findLastIndex functions
 614    function createPredicateIndexFinder(dir) {
 615      return function(array, predicate, context) {
 616        predicate = cb(predicate, context);
 617        var length = getLength(array);
 618        var index = dir > 0 ? 0 : length - 1;
 619        for (; index >= 0 && index < length; index += dir) {
 620          if (predicate(array[index], index, array)) return index;
 621        }
 622        return -1;
 623      };
 624    }
 625  
 626    // Returns the first index on an array-like that passes a predicate test
 627    _.findIndex = createPredicateIndexFinder(1);
 628    _.findLastIndex = createPredicateIndexFinder(-1);
 629  
 630    // Use a comparator function to figure out the smallest index at which
 631    // an object should be inserted so as to maintain order. Uses binary search.
 632    _.sortedIndex = function(array, obj, iteratee, context) {
 633      iteratee = cb(iteratee, context, 1);
 634      var value = iteratee(obj);
 635      var low = 0, high = getLength(array);
 636      while (low < high) {
 637        var mid = Math.floor((low + high) / 2);
 638        if (iteratee(array[mid]) < value) low = mid + 1; else high = mid;
 639      }
 640      return low;
 641    };
 642  
 643    // Generator function to create the indexOf and lastIndexOf functions
 644    function createIndexFinder(dir, predicateFind, sortedIndex) {
 645      return function(array, item, idx) {
 646        var i = 0, length = getLength(array);
 647        if (typeof idx == 'number') {
 648          if (dir > 0) {
 649              i = idx >= 0 ? idx : Math.max(idx + length, i);
 650          } else {
 651              length = idx >= 0 ? Math.min(idx + 1, length) : idx + length + 1;
 652          }
 653        } else if (sortedIndex && idx && length) {
 654          idx = sortedIndex(array, item);
 655          return array[idx] === item ? idx : -1;
 656        }
 657        if (item !== item) {
 658          idx = predicateFind(slice.call(array, i, length), _.isNaN);
 659          return idx >= 0 ? idx + i : -1;
 660        }
 661        for (idx = dir > 0 ? i : length - 1; idx >= 0 && idx < length; idx += dir) {
 662          if (array[idx] === item) return idx;
 663        }
 664        return -1;
 665      };
 666    }
 667  
 668    // Return the position of the first occurrence of an item in an array,
 669    // or -1 if the item is not included in the array.
 670    // If the array is large and already in sort order, pass `true`
 671    // for **isSorted** to use binary search.
 672    _.indexOf = createIndexFinder(1, _.findIndex, _.sortedIndex);
 673    _.lastIndexOf = createIndexFinder(-1, _.findLastIndex);
 674  
 675    // Generate an integer Array containing an arithmetic progression. A port of
 676    // the native Python `range()` function. See
 677    // [the Python documentation](http://docs.python.org/library/functions.html#range).
 678    _.range = function(start, stop, step) {
 679      if (stop == null) {
 680        stop = start || 0;
 681        start = 0;
 682      }
 683      step = step || 1;
 684  
 685      var length = Math.max(Math.ceil((stop - start) / step), 0);
 686      var range = Array(length);
 687  
 688      for (var idx = 0; idx < length; idx++, start += step) {
 689        range[idx] = start;
 690      }
 691  
 692      return range;
 693    };
 694  
 695    // Function (ahem) Functions
 696    // ------------------
 697  
 698    // Determines whether to execute a function as a constructor
 699    // or a normal function with the provided arguments
 700    var executeBound = function(sourceFunc, boundFunc, context, callingContext, args) {
 701      if (!(callingContext instanceof boundFunc)) return sourceFunc.apply(context, args);
 702      var self = baseCreate(sourceFunc.prototype);
 703      var result = sourceFunc.apply(self, args);
 704      if (_.isObject(result)) return result;
 705      return self;
 706    };
 707  
 708    // Create a function bound to a given object (assigning `this`, and arguments,
 709    // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
 710    // available.
 711    _.bind = function(func, context) {
 712      if (nativeBind && func.bind === nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
 713      if (!_.isFunction(func)) throw new TypeError('Bind must be called on a function');
 714      var args = slice.call(arguments, 2);
 715      var bound = function() {
 716        return executeBound(func, bound, context, this, args.concat(slice.call(arguments)));
 717      };
 718      return bound;
 719    };
 720  
 721    // Partially apply a function by creating a version that has had some of its
 722    // arguments pre-filled, without changing its dynamic `this` context. _ acts
 723    // as a placeholder, allowing any combination of arguments to be pre-filled.
 724    _.partial = function(func) {
 725      var boundArgs = slice.call(arguments, 1);
 726      var bound = function() {
 727        var position = 0, length = boundArgs.length;
 728        var args = Array(length);
 729        for (var i = 0; i < length; i++) {
 730          args[i] = boundArgs[i] === _ ? arguments[position++] : boundArgs[i];
 731        }
 732        while (position < arguments.length) args.push(arguments[position++]);
 733        return executeBound(func, bound, this, this, args);
 734      };
 735      return bound;
 736    };
 737  
 738    // Bind a number of an object's methods to that object. Remaining arguments
 739    // are the method names to be bound. Useful for ensuring that all callbacks
 740    // defined on an object belong to it.
 741    _.bindAll = function(obj) {
 742      var i, length = arguments.length, key;
 743      if (length <= 1) throw new Error('bindAll must be passed function names');
 744      for (i = 1; i < length; i++) {
 745        key = arguments[i];
 746        obj[key] = _.bind(obj[key], obj);
 747      }
 748      return obj;
 749    };
 750  
 751    // Memoize an expensive function by storing its results.
 752    _.memoize = function(func, hasher) {
 753      var memoize = function(key) {
 754        var cache = memoize.cache;
 755        var address = '' + (hasher ? hasher.apply(this, arguments) : key);
 756        if (!_.has(cache, address)) cache[address] = func.apply(this, arguments);
 757        return cache[address];
 758      };
 759      memoize.cache = {};
 760      return memoize;
 761    };
 762  
 763    // Delays a function for the given number of milliseconds, and then calls
 764    // it with the arguments supplied.
 765    _.delay = function(func, wait) {
 766      var args = slice.call(arguments, 2);
 767      return setTimeout(function(){
 768        return func.apply(null, args);
 769      }, wait);
 770    };
 771  
 772    // Defers a function, scheduling it to run after the current call stack has
 773    // cleared.
 774    _.defer = _.partial(_.delay, _, 1);
 775  
 776    // Returns a function, that, when invoked, will only be triggered at most once
 777    // during a given window of time. Normally, the throttled function will run
 778    // as much as it can, without ever going more than once per `wait` duration;
 779    // but if you'd like to disable the execution on the leading edge, pass
 780    // `{leading: false}`. To disable execution on the trailing edge, ditto.
 781    _.throttle = function(func, wait, options) {
 782      var context, args, result;
 783      var timeout = null;
 784      var previous = 0;
 785      if (!options) options = {};
 786      var later = function() {
 787        previous = options.leading === false ? 0 : _.now();
 788        timeout = null;
 789        result = func.apply(context, args);
 790        if (!timeout) context = args = null;
 791      };
 792      return function() {
 793        var now = _.now();
 794        if (!previous && options.leading === false) previous = now;
 795        var remaining = wait - (now - previous);
 796        context = this;
 797        args = arguments;
 798        if (remaining <= 0 || remaining > wait) {
 799          if (timeout) {
 800            clearTimeout(timeout);
 801            timeout = null;
 802          }
 803          previous = now;
 804          result = func.apply(context, args);
 805          if (!timeout) context = args = null;
 806        } else if (!timeout && options.trailing !== false) {
 807          timeout = setTimeout(later, remaining);
 808        }
 809        return result;
 810      };
 811    };
 812  
 813    // Returns a function, that, as long as it continues to be invoked, will not
 814    // be triggered. The function will be called after it stops being called for
 815    // N milliseconds. If `immediate` is passed, trigger the function on the
 816    // leading edge, instead of the trailing.
 817    _.debounce = function(func, wait, immediate) {
 818      var timeout, args, context, timestamp, result;
 819  
 820      var later = function() {
 821        var last = _.now() - timestamp;
 822  
 823        if (last < wait && last >= 0) {
 824          timeout = setTimeout(later, wait - last);
 825        } else {
 826          timeout = null;
 827          if (!immediate) {
 828            result = func.apply(context, args);
 829            if (!timeout) context = args = null;
 830          }
 831        }
 832      };
 833  
 834      return function() {
 835        context = this;
 836        args = arguments;
 837        timestamp = _.now();
 838        var callNow = immediate && !timeout;
 839        if (!timeout) timeout = setTimeout(later, wait);
 840        if (callNow) {
 841          result = func.apply(context, args);
 842          context = args = null;
 843        }
 844  
 845        return result;
 846      };
 847    };
 848  
 849    // Returns the first function passed as an argument to the second,
 850    // allowing you to adjust arguments, run code before and after, and
 851    // conditionally execute the original function.
 852    _.wrap = function(func, wrapper) {
 853      return _.partial(wrapper, func);
 854    };
 855  
 856    // Returns a negated version of the passed-in predicate.
 857    _.negate = function(predicate) {
 858      return function() {
 859        return !predicate.apply(this, arguments);
 860      };
 861    };
 862  
 863    // Returns a function that is the composition of a list of functions, each
 864    // consuming the return value of the function that follows.
 865    _.compose = function() {
 866      var args = arguments;
 867      var start = args.length - 1;
 868      return function() {
 869        var i = start;
 870        var result = args[start].apply(this, arguments);
 871        while (i--) result = args[i].call(this, result);
 872        return result;
 873      };
 874    };
 875  
 876    // Returns a function that will only be executed on and after the Nth call.
 877    _.after = function(times, func) {
 878      return function() {
 879        if (--times < 1) {
 880          return func.apply(this, arguments);
 881        }
 882      };
 883    };
 884  
 885    // Returns a function that will only be executed up to (but not including) the Nth call.
 886    _.before = function(times, func) {
 887      var memo;
 888      return function() {
 889        if (--times > 0) {
 890          memo = func.apply(this, arguments);
 891        }
 892        if (times <= 1) func = null;
 893        return memo;
 894      };
 895    };
 896  
 897    // Returns a function that will be executed at most one time, no matter how
 898    // often you call it. Useful for lazy initialization.
 899    _.once = _.partial(_.before, 2);
 900  
 901    // Object Functions
 902    // ----------------
 903  
 904    // Keys in IE < 9 that won't be iterated by `for key in ...` and thus missed.
 905    var hasEnumBug = !{toString: null}.propertyIsEnumerable('toString');
 906    var nonEnumerableProps = ['valueOf', 'isPrototypeOf', 'toString',
 907                        'propertyIsEnumerable', 'hasOwnProperty', 'toLocaleString'];
 908  
 909    function collectNonEnumProps(obj, keys) {
 910      var nonEnumIdx = nonEnumerableProps.length;
 911      var constructor = obj.constructor;
 912      var proto = (_.isFunction(constructor) && constructor.prototype) || ObjProto;
 913  
 914      // Constructor is a special case.
 915      var prop = 'constructor';
 916      if (_.has(obj, prop) && !_.contains(keys, prop)) keys.push(prop);
 917  
 918      while (nonEnumIdx--) {
 919        prop = nonEnumerableProps[nonEnumIdx];
 920        if (prop in obj && obj[prop] !== proto[prop] && !_.contains(keys, prop)) {
 921          keys.push(prop);
 922        }
 923      }
 924    }
 925  
 926    // Retrieve the names of an object's own properties.
 927    // Delegates to **ECMAScript 5**'s native `Object.keys`
 928    _.keys = function(obj) {
 929      if (!_.isObject(obj)) return [];
 930      if (nativeKeys) return nativeKeys(obj);
 931      var keys = [];
 932      for (var key in obj) if (_.has(obj, key)) keys.push(key);
 933      // Ahem, IE < 9.
 934      if (hasEnumBug) collectNonEnumProps(obj, keys);
 935      return keys;
 936    };
 937  
 938    // Retrieve all the property names of an object.
 939    _.allKeys = function(obj) {
 940      if (!_.isObject(obj)) return [];
 941      var keys = [];
 942      for (var key in obj) keys.push(key);
 943      // Ahem, IE < 9.
 944      if (hasEnumBug) collectNonEnumProps(obj, keys);
 945      return keys;
 946    };
 947  
 948    // Retrieve the values of an object's properties.
 949    _.values = function(obj) {
 950      var keys = _.keys(obj);
 951      var length = keys.length;
 952      var values = Array(length);
 953      for (var i = 0; i < length; i++) {
 954        values[i] = obj[keys[i]];
 955      }
 956      return values;
 957    };
 958  
 959    // Returns the results of applying the iteratee to each element of the object
 960    // In contrast to _.map it returns an object
 961    _.mapObject = function(obj, iteratee, context) {
 962      iteratee = cb(iteratee, context);
 963      var keys =  _.keys(obj),
 964            length = keys.length,
 965            results = {},
 966            currentKey;
 967        for (var index = 0; index < length; index++) {
 968          currentKey = keys[index];
 969          results[currentKey] = iteratee(obj[currentKey], currentKey, obj);
 970        }
 971        return results;
 972    };
 973  
 974    // Convert an object into a list of `[key, value]` pairs.
 975    _.pairs = function(obj) {
 976      var keys = _.keys(obj);
 977      var length = keys.length;
 978      var pairs = Array(length);
 979      for (var i = 0; i < length; i++) {
 980        pairs[i] = [keys[i], obj[keys[i]]];
 981      }
 982      return pairs;
 983    };
 984  
 985    // Invert the keys and values of an object. The values must be serializable.
 986    _.invert = function(obj) {
 987      var result = {};
 988      var keys = _.keys(obj);
 989      for (var i = 0, length = keys.length; i < length; i++) {
 990        result[obj[keys[i]]] = keys[i];
 991      }
 992      return result;
 993    };
 994  
 995    // Return a sorted list of the function names available on the object.
 996    // Aliased as `methods`
 997    _.functions = _.methods = function(obj) {
 998      var names = [];
 999      for (var key in obj) {
1000        if (_.isFunction(obj[key])) names.push(key);
1001      }
1002      return names.sort();
1003    };
1004  
1005    // Extend a given object with all the properties in passed-in object(s).
1006    _.extend = createAssigner(_.allKeys);
1007  
1008    // Assigns a given object with all the own properties in the passed-in object(s)
1009    // (https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign)
1010    _.extendOwn = _.assign = createAssigner(_.keys);
1011  
1012    // Returns the first key on an object that passes a predicate test
1013    _.findKey = function(obj, predicate, context) {
1014      predicate = cb(predicate, context);
1015      var keys = _.keys(obj), key;
1016      for (var i = 0, length = keys.length; i < length; i++) {
1017        key = keys[i];
1018        if (predicate(obj[key], key, obj)) return key;
1019      }
1020    };
1021  
1022    // Return a copy of the object only containing the whitelisted properties.
1023    _.pick = function(object, oiteratee, context) {
1024      var result = {}, obj = object, iteratee, keys;
1025      if (obj == null) return result;
1026      if (_.isFunction(oiteratee)) {
1027        keys = _.allKeys(obj);
1028        iteratee = optimizeCb(oiteratee, context);
1029      } else {
1030        keys = flatten(arguments, false, false, 1);
1031        iteratee = function(value, key, obj) { return key in obj; };
1032        obj = Object(obj);
1033      }
1034      for (var i = 0, length = keys.length; i < length; i++) {
1035        var key = keys[i];
1036        var value = obj[key];
1037        if (iteratee(value, key, obj)) result[key] = value;
1038      }
1039      return result;
1040    };
1041  
1042     // Return a copy of the object without the blacklisted properties.
1043    _.omit = function(obj, iteratee, context) {
1044      if (_.isFunction(iteratee)) {
1045        iteratee = _.negate(iteratee);
1046      } else {
1047        var keys = _.map(flatten(arguments, false, false, 1), String);
1048        iteratee = function(value, key) {
1049          return !_.contains(keys, key);
1050        };
1051      }
1052      return _.pick(obj, iteratee, context);
1053    };
1054  
1055    // Fill in a given object with default properties.
1056    _.defaults = createAssigner(_.allKeys, true);
1057  
1058    // Creates an object that inherits from the given prototype object.
1059    // If additional properties are provided then they will be added to the
1060    // created object.
1061    _.create = function(prototype, props) {
1062      var result = baseCreate(prototype);
1063      if (props) _.extendOwn(result, props);
1064      return result;
1065    };
1066  
1067    // Create a (shallow-cloned) duplicate of an object.
1068    _.clone = function(obj) {
1069      if (!_.isObject(obj)) return obj;
1070      return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
1071    };
1072  
1073    // Invokes interceptor with the obj, and then returns obj.
1074    // The primary purpose of this method is to "tap into" a method chain, in
1075    // order to perform operations on intermediate results within the chain.
1076    _.tap = function(obj, interceptor) {
1077      interceptor(obj);
1078      return obj;
1079    };
1080  
1081    // Returns whether an object has a given set of `key:value` pairs.
1082    _.isMatch = function(object, attrs) {
1083      var keys = _.keys(attrs), length = keys.length;
1084      if (object == null) return !length;
1085      var obj = Object(object);
1086      for (var i = 0; i < length; i++) {
1087        var key = keys[i];
1088        if (attrs[key] !== obj[key] || !(key in obj)) return false;
1089      }
1090      return true;
1091    };
1092  
1093  
1094    // Internal recursive comparison function for `isEqual`.
1095    var eq = function(a, b, aStack, bStack) {
1096      // Identical objects are equal. `0 === -0`, but they aren't identical.
1097      // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
1098      if (a === b) return a !== 0 || 1 / a === 1 / b;
1099      // A strict comparison is necessary because `null == undefined`.
1100      if (a == null || b == null) return a === b;
1101      // Unwrap any wrapped objects.
1102      if (a instanceof _) a = a._wrapped;
1103      if (b instanceof _) b = b._wrapped;
1104      // Compare `[[Class]]` names.
1105      var className = toString.call(a);
1106      if (className !== toString.call(b)) return false;
1107      switch (className) {
1108        // Strings, numbers, regular expressions, dates, and booleans are compared by value.
1109        case '[object RegExp]':
1110        // RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
1111        case '[object String]':
1112          // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
1113          // equivalent to `new String("5")`.
1114          return '' + a === '' + b;
1115        case '[object Number]':
1116          // `NaN`s are equivalent, but non-reflexive.
1117          // Object(NaN) is equivalent to NaN
1118          if (+a !== +a) return +b !== +b;
1119          // An `egal` comparison is performed for other numeric values.
1120          return +a === 0 ? 1 / +a === 1 / b : +a === +b;
1121        case '[object Date]':
1122        case '[object Boolean]':
1123          // Coerce dates and booleans to numeric primitive values. Dates are compared by their
1124          // millisecond representations. Note that invalid dates with millisecond representations
1125          // of `NaN` are not equivalent.
1126          return +a === +b;
1127      }
1128  
1129      var areArrays = className === '[object Array]';
1130      if (!areArrays) {
1131        if (typeof a != 'object' || typeof b != 'object') return false;
1132  
1133        // Objects with different constructors are not equivalent, but `Object`s or `Array`s
1134        // from different frames are.
1135        var aCtor = a.constructor, bCtor = b.constructor;
1136        if (aCtor !== bCtor && !(_.isFunction(aCtor) && aCtor instanceof aCtor &&
1137                                 _.isFunction(bCtor) && bCtor instanceof bCtor)
1138                            && ('constructor' in a && 'constructor' in b)) {
1139          return false;
1140        }
1141      }
1142      // Assume equality for cyclic structures. The algorithm for detecting cyclic
1143      // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
1144  
1145      // Initializing stack of traversed objects.
1146      // It's done here since we only need them for objects and arrays comparison.
1147      aStack = aStack || [];
1148      bStack = bStack || [];
1149      var length = aStack.length;
1150      while (length--) {
1151        // Linear search. Performance is inversely proportional to the number of
1152        // unique nested structures.
1153        if (aStack[length] === a) return bStack[length] === b;
1154      }
1155  
1156      // Add the first object to the stack of traversed objects.
1157      aStack.push(a);
1158      bStack.push(b);
1159  
1160      // Recursively compare objects and arrays.
1161      if (areArrays) {
1162        // Compare array lengths to determine if a deep comparison is necessary.
1163        length = a.length;
1164        if (length !== b.length) return false;
1165        // Deep compare the contents, ignoring non-numeric properties.
1166        while (length--) {
1167          if (!eq(a[length], b[length], aStack, bStack)) return false;
1168        }
1169      } else {
1170        // Deep compare objects.
1171        var keys = _.keys(a), key;
1172        length = keys.length;
1173        // Ensure that both objects contain the same number of properties before comparing deep equality.
1174        if (_.keys(b).length !== length) return false;
1175        while (length--) {
1176          // Deep compare each member
1177          key = keys[length];
1178          if (!(_.has(b, key) && eq(a[key], b[key], aStack, bStack))) return false;
1179        }
1180      }
1181      // Remove the first object from the stack of traversed objects.
1182      aStack.pop();
1183      bStack.pop();
1184      return true;
1185    };
1186  
1187    // Perform a deep comparison to check if two objects are equal.
1188    _.isEqual = function(a, b) {
1189      return eq(a, b);
1190    };
1191  
1192    // Is a given array, string, or object empty?
1193    // An "empty" object has no enumerable own-properties.
1194    _.isEmpty = function(obj) {
1195      if (obj == null) return true;
1196      if (isArrayLike(obj) && (_.isArray(obj) || _.isString(obj) || _.isArguments(obj))) return obj.length === 0;
1197      return _.keys(obj).length === 0;
1198    };
1199  
1200    // Is a given value a DOM element?
1201    _.isElement = function(obj) {
1202      return !!(obj && obj.nodeType === 1);
1203    };
1204  
1205    // Is a given value an array?
1206    // Delegates to ECMA5's native Array.isArray
1207    _.isArray = nativeIsArray || function(obj) {
1208      return toString.call(obj) === '[object Array]';
1209    };
1210  
1211    // Is a given variable an object?
1212    _.isObject = function(obj) {
1213      var type = typeof obj;
1214      return type === 'function' || type === 'object' && !!obj;
1215    };
1216  
1217    // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
1218    _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error'], function(name) {
1219      _['is' + name] = function(obj) {
1220        return toString.call(obj) === '[object ' + name + ']';
1221      };
1222    });
1223  
1224    // Define a fallback version of the method in browsers (ahem, IE < 9), where
1225    // there isn't any inspectable "Arguments" type.
1226    if (!_.isArguments(arguments)) {
1227      _.isArguments = function(obj) {
1228        return _.has(obj, 'callee');
1229      };
1230    }
1231  
1232    // Optimize `isFunction` if appropriate. Work around some typeof bugs in old v8,
1233    // IE 11 (#1621), and in Safari 8 (#1929).
1234    if (typeof /./ != 'function' && typeof Int8Array != 'object') {
1235      _.isFunction = function(obj) {
1236        return typeof obj == 'function' || false;
1237      };
1238    }
1239  
1240    // Is a given object a finite number?
1241    _.isFinite = function(obj) {
1242      return isFinite(obj) && !isNaN(parseFloat(obj));
1243    };
1244  
1245    // Is the given value `NaN`? (NaN is the only number which does not equal itself).
1246    _.isNaN = function(obj) {
1247      return _.isNumber(obj) && obj !== +obj;
1248    };
1249  
1250    // Is a given value a boolean?
1251    _.isBoolean = function(obj) {
1252      return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
1253    };
1254  
1255    // Is a given value equal to null?
1256    _.isNull = function(obj) {
1257      return obj === null;
1258    };
1259  
1260    // Is a given variable undefined?
1261    _.isUndefined = function(obj) {
1262      return obj === void 0;
1263    };
1264  
1265    // Shortcut function for checking if an object has a given property directly
1266    // on itself (in other words, not on a prototype).
1267    _.has = function(obj, key) {
1268      return obj != null && hasOwnProperty.call(obj, key);
1269    };
1270  
1271    // Utility Functions
1272    // -----------------
1273  
1274    // Run Underscore.js in *noConflict* mode, returning the `_` variable to its
1275    // previous owner. Returns a reference to the Underscore object.
1276    _.noConflict = function() {
1277      root._ = previousUnderscore;
1278      return this;
1279    };
1280  
1281    // Keep the identity function around for default iteratees.
1282    _.identity = function(value) {
1283      return value;
1284    };
1285  
1286    // Predicate-generating functions. Often useful outside of Underscore.
1287    _.constant = function(value) {
1288      return function() {
1289        return value;
1290      };
1291    };
1292  
1293    _.noop = function(){};
1294  
1295    _.property = property;
1296  
1297    // Generates a function for a given object that returns a given property.
1298    _.propertyOf = function(obj) {
1299      return obj == null ? function(){} : function(key) {
1300        return obj[key];
1301      };
1302    };
1303  
1304    // Returns a predicate for checking whether an object has a given set of
1305    // `key:value` pairs.
1306    _.matcher = _.matches = function(attrs) {
1307      attrs = _.extendOwn({}, attrs);
1308      return function(obj) {
1309        return _.isMatch(obj, attrs);
1310      };
1311    };
1312  
1313    // Run a function **n** times.
1314    _.times = function(n, iteratee, context) {
1315      var accum = Array(Math.max(0, n));
1316      iteratee = optimizeCb(iteratee, context, 1);
1317      for (var i = 0; i < n; i++) accum[i] = iteratee(i);
1318      return accum;
1319    };
1320  
1321    // Return a random integer between min and max (inclusive).
1322    _.random = function(min, max) {
1323      if (max == null) {
1324        max = min;
1325        min = 0;
1326      }
1327      return min + Math.floor(Math.random() * (max - min + 1));
1328    };
1329  
1330    // A (possibly faster) way to get the current timestamp as an integer.
1331    _.now = Date.now || function() {
1332      return new Date().getTime();
1333    };
1334  
1335     // List of HTML entities for escaping.
1336    var escapeMap = {
1337      '&': '&amp;',
1338      '<': '&lt;',
1339      '>': '&gt;',
1340      '"': '&quot;',
1341      "'": '&#x27;',
1342      '`': '&#x60;'
1343    };
1344    var unescapeMap = _.invert(escapeMap);
1345  
1346    // Functions for escaping and unescaping strings to/from HTML interpolation.
1347    var createEscaper = function(map) {
1348      var escaper = function(match) {
1349        return map[match];
1350      };
1351      // Regexes for identifying a key that needs to be escaped
1352      var source = '(?:' + _.keys(map).join('|') + ')';
1353      var testRegexp = RegExp(source);
1354      var replaceRegexp = RegExp(source, 'g');
1355      return function(string) {
1356        string = string == null ? '' : '' + string;
1357        return testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
1358      };
1359    };
1360    _.escape = createEscaper(escapeMap);
1361    _.unescape = createEscaper(unescapeMap);
1362  
1363    // If the value of the named `property` is a function then invoke it with the
1364    // `object` as context; otherwise, return it.
1365    _.result = function(object, property, fallback) {
1366      var value = object == null ? void 0 : object[property];
1367      if (value === void 0) {
1368        value = fallback;
1369      }
1370      return _.isFunction(value) ? value.call(object) : value;
1371    };
1372  
1373    // Generate a unique integer id (unique within the entire client session).
1374    // Useful for temporary DOM ids.
1375    var idCounter = 0;
1376    _.uniqueId = function(prefix) {
1377      var id = ++idCounter + '';
1378      return prefix ? prefix + id : id;
1379    };
1380  
1381    // By default, Underscore uses ERB-style template delimiters, change the
1382    // following template settings to use alternative delimiters.
1383    _.templateSettings = {
1384      evaluate    : /<%([\s\S]+?)%>/g,
1385      interpolate : /<%=([\s\S]+?)%>/g,
1386      escape      : /<%-([\s\S]+?)%>/g
1387    };
1388  
1389    // When customizing `templateSettings`, if you don't want to define an
1390    // interpolation, evaluation or escaping regex, we need one that is
1391    // guaranteed not to match.
1392    var noMatch = /(.)^/;
1393  
1394    // Certain characters need to be escaped so that they can be put into a
1395    // string literal.
1396    var escapes = {
1397      "'":      "'",
1398      '\\':     '\\',
1399      '\r':     'r',
1400      '\n':     'n',
1401      '\u2028': 'u2028',
1402      '\u2029': 'u2029'
1403    };
1404  
1405    var escaper = /\\|'|\r|\n|\u2028|\u2029/g;
1406  
1407    var escapeChar = function(match) {
1408      return '\\' + escapes[match];
1409    };
1410  
1411    // JavaScript micro-templating, similar to John Resig's implementation.
1412    // Underscore templating handles arbitrary delimiters, preserves whitespace,
1413    // and correctly escapes quotes within interpolated code.
1414    // NB: `oldSettings` only exists for backwards compatibility.
1415    _.template = function(text, settings, oldSettings) {
1416      if (!settings && oldSettings) settings = oldSettings;
1417      settings = _.defaults({}, settings, _.templateSettings);
1418  
1419      // Combine delimiters into one regular expression via alternation.
1420      var matcher = RegExp([
1421        (settings.escape || noMatch).source,
1422        (settings.interpolate || noMatch).source,
1423        (settings.evaluate || noMatch).source
1424      ].join('|') + '|$', 'g');
1425  
1426      // Compile the template source, escaping string literals appropriately.
1427      var index = 0;
1428      var source = "__p+='";
1429      text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
1430        source += text.slice(index, offset).replace(escaper, escapeChar);
1431        index = offset + match.length;
1432  
1433        if (escape) {
1434          source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
1435        } else if (interpolate) {
1436          source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
1437        } else if (evaluate) {
1438          source += "';\n" + evaluate + "\n__p+='";
1439        }
1440  
1441        // Adobe VMs need the match returned to produce the correct offest.
1442        return match;
1443      });
1444      source += "';\n";
1445  
1446      // If a variable is not specified, place data values in local scope.
1447      if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';
1448  
1449      source = "var __t,__p='',__j=Array.prototype.join," +
1450        "print=function(){__p+=__j.call(arguments,'');};\n" +
1451        source + 'return __p;\n';
1452  
1453      try {
1454        var render = new Function(settings.variable || 'obj', '_', source);
1455      } catch (e) {
1456        e.source = source;
1457        throw e;
1458      }
1459  
1460      var template = function(data) {
1461        return render.call(this, data, _);
1462      };
1463  
1464      // Provide the compiled source as a convenience for precompilation.
1465      var argument = settings.variable || 'obj';
1466      template.source = 'function(' + argument + '){\n' + source + '}';
1467  
1468      return template;
1469    };
1470  
1471    // Add a "chain" function. Start chaining a wrapped Underscore object.
1472    _.chain = function(obj) {
1473      var instance = _(obj);
1474      instance._chain = true;
1475      return instance;
1476    };
1477  
1478    // OOP
1479    // ---------------
1480    // If Underscore is called as a function, it returns a wrapped object that
1481    // can be used OO-style. This wrapper holds altered versions of all the
1482    // underscore functions. Wrapped objects may be chained.
1483  
1484    // Helper function to continue chaining intermediate results.
1485    var result = function(instance, obj) {
1486      return instance._chain ? _(obj).chain() : obj;
1487    };
1488  
1489    // Add your own custom functions to the Underscore object.
1490    _.mixin = function(obj) {
1491      _.each(_.functions(obj), function(name) {
1492        var func = _[name] = obj[name];
1493        _.prototype[name] = function() {
1494          var args = [this._wrapped];
1495          push.apply(args, arguments);
1496          return result(this, func.apply(_, args));
1497        };
1498      });
1499    };
1500  
1501    // Add all of the Underscore functions to the wrapper object.
1502    _.mixin(_);
1503  
1504    // Add all mutator Array functions to the wrapper.
1505    _.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
1506      var method = ArrayProto[name];
1507      _.prototype[name] = function() {
1508        var obj = this._wrapped;
1509        method.apply(obj, arguments);
1510        if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0];
1511        return result(this, obj);
1512      };
1513    });
1514  
1515    // Add all accessor Array functions to the wrapper.
1516    _.each(['concat', 'join', 'slice'], function(name) {
1517      var method = ArrayProto[name];
1518      _.prototype[name] = function() {
1519        return result(this, method.apply(this._wrapped, arguments));
1520      };
1521    });
1522  
1523    // Extracts the result from a wrapped and chained object.
1524    _.prototype.value = function() {
1525      return this._wrapped;
1526    };
1527  
1528    // Provide unwrapping proxy for some methods used in engine operations
1529    // such as arithmetic and JSON stringification.
1530    _.prototype.valueOf = _.prototype.toJSON = _.prototype.value;
1531  
1532    _.prototype.toString = function() {
1533      return '' + this._wrapped;
1534    };
1535  
1536    // AMD registration happens at the end for compatibility with AMD loaders
1537    // that may not enforce next-turn semantics on modules. Even though general
1538    // practice for AMD registration is to be anonymous, underscore registers
1539    // as a named module because, like jQuery, it is a base library that is
1540    // popular enough to be bundled in a third party lib, but not be part of
1541    // an AMD load request. Those cases could generate an error when an
1542    // anonymous define() is called outside of a loader request.
1543    if (typeof define === 'function' && define.amd) {
1544      define('underscore', [], function() {
1545        return _;
1546      });
1547    }
1548  }.call(this));


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