1  var arrayReduce = require('./_arrayReduce'),
 2      baseEach = require('./_baseEach'),
 3      baseIteratee = require('./_baseIteratee'),
 4      baseReduce = require('./_baseReduce'),
 5      isArray = require('./isArray');
 6  
 7  /**
 8   * Reduces `collection` to a value which is the accumulated result of running
 9   * each element in `collection` thru `iteratee`, where each successive
10   * invocation is supplied the return value of the previous. If `accumulator`
11   * is not given, the first element of `collection` is used as the initial
12   * value. The iteratee is invoked with four arguments:
13   * (accumulator, value, index|key, collection).
14   *
15   * Many lodash methods are guarded to work as iteratees for methods like
16   * `_.reduce`, `_.reduceRight`, and `_.transform`.
17   *
18   * The guarded methods are:
19   * `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `orderBy`,
20   * and `sortBy`
21   *
22   * @static
23   * @memberOf _
24   * @since 0.1.0
25   * @category Collection
26   * @param {Array|Object} collection The collection to iterate over.
27   * @param {Function} [iteratee=_.identity] The function invoked per iteration.
28   * @param {*} [accumulator] The initial value.
29   * @returns {*} Returns the accumulated value.
30   * @see _.reduceRight
31   * @example
32   *
33   * _.reduce([1, 2], function(sum, n) {
34   *   return sum + n;
35   * }, 0);
36   * // => 3
37   *
38   * _.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
39   *   (result[value] || (result[value] = [])).push(key);
40   *   return result;
41   * }, {});
42   * // => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)
43   */
44  function reduce(collection, iteratee, accumulator) {
45    var func = isArray(collection) ? arrayReduce : baseReduce,
46        initAccum = arguments.length < 3;
47  
48    return func(collection, baseIteratee(iteratee, 4), accumulator, initAccum, baseEach);
49  }
50  
51  module.exports = reduce;