1 var arrayReduce = require('./_arrayReduce'),
2 baseEach = require('./_baseEach'),
3 baseIteratee = require('./_baseIteratee'),
4 baseReduce = require('./_baseReduce'),
5 isArray = require('./isArray');
8 * Reduces `collection` to a value which is the accumulated result of running
9 * each element in `collection` through `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).
15 * Many lodash methods are guarded to work as iteratees for methods like
16 * `_.reduce`, `_.reduceRight`, and `_.transform`.
18 * The guarded methods are:
19 * `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `orderBy`,
24 * @category Collection
25 * @param {Array|Object} collection The collection to iterate over.
26 * @param {Function} [iteratee=_.identity] The function invoked per iteration.
27 * @param {*} [accumulator] The initial value.
28 * @returns {*} Returns the accumulated value.
31 * _.reduce([1, 2], function(sum, n) {
36 * _.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
37 * (result[value] || (result[value] = [])).push(key);
40 * // => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)
42 function reduce(collection, iteratee, accumulator) {
43 var func = isArray(collection) ? arrayReduce : baseReduce,
44 initAccum = arguments.length < 3;
46 return func(collection, baseIteratee(iteratee, 4), accumulator, initAccum, baseEach);
49 module.exports = reduce;