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52 lines
1.8 KiB
JavaScript
52 lines
1.8 KiB
JavaScript
6 years ago
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var arrayReduce = require('./_arrayReduce'),
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baseEach = require('./_baseEach'),
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baseIteratee = require('./_baseIteratee'),
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baseReduce = require('./_baseReduce'),
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isArray = require('./isArray');
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/**
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* Reduces `collection` to a value which is the accumulated result of running
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* each element in `collection` thru `iteratee`, where each successive
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* invocation is supplied the return value of the previous. If `accumulator`
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* is not given, the first element of `collection` is used as the initial
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* value. The iteratee is invoked with four arguments:
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* (accumulator, value, index|key, collection).
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*
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* Many lodash methods are guarded to work as iteratees for methods like
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* `_.reduce`, `_.reduceRight`, and `_.transform`.
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*
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* The guarded methods are:
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* `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `orderBy`,
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* and `sortBy`
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*
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* @static
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* @memberOf _
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* @since 0.1.0
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* @category Collection
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* @param {Array|Object} collection The collection to iterate over.
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* @param {Function} [iteratee=_.identity] The function invoked per iteration.
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* @param {*} [accumulator] The initial value.
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* @returns {*} Returns the accumulated value.
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* @see _.reduceRight
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* @example
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*
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* _.reduce([1, 2], function(sum, n) {
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* return sum + n;
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* }, 0);
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* // => 3
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*
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* _.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
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* (result[value] || (result[value] = [])).push(key);
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* return result;
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* }, {});
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* // => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)
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*/
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function reduce(collection, iteratee, accumulator) {
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var func = isArray(collection) ? arrayReduce : baseReduce,
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initAccum = arguments.length < 3;
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return func(collection, baseIteratee(iteratee, 4), accumulator, initAccum, baseEach);
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}
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module.exports = reduce;
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