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