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81 lines
2.9 KiB
JavaScript
81 lines
2.9 KiB
JavaScript
/**
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* lodash 3.0.0 (Custom Build) <https://lodash.com/>
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* Build: `lodash modern modularize exports="npm" -o ./`
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* Copyright 2012-2015 The Dojo Foundation <http://dojofoundation.org/>
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* Based on Underscore.js 1.7.0 <http://underscorejs.org/LICENSE>
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* Copyright 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
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* Available under MIT license <https://lodash.com/license>
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*/
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var baseCallback = require('lodash._basecallback'),
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baseEach = require('lodash._baseeach'),
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baseReduce = require('lodash._basereduce'),
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isArray = require('lodash.isarray');
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/**
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* A specialized version of `_.reduce` for arrays without support for callback
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* shorthands or `this` binding.
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*
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* @private
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* @param {Array} array The array to iterate over.
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* @param {Function} iteratee The function invoked per iteration.
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* @param {*} [accumulator] The initial value.
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* @param {boolean} [initFromArray] Specify using the first element of `array`
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* as the initial value.
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* @returns {*} Returns the accumulated value.
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*/
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function arrayReduce(array, iteratee, accumulator, initFromArray) {
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var index = -1,
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length = array.length;
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if (initFromArray && length) {
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accumulator = array[++index];
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}
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while (++index < length) {
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accumulator = iteratee(accumulator, array[index], index, array);
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}
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return accumulator;
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}
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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` through `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 provided the first element of `collection` is used as the initial
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* value. The `iteratee` is bound to `thisArg`and 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 interatees 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`, `merge`, and `sortAllBy`
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*
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* @static
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* @memberOf _
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* @alias foldl, inject
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* @category Collection
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* @param {Array|Object|string} 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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* @param {*} [thisArg] The `this` binding of `iteratee`.
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* @returns {*} Returns the accumulated value.
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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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* });
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* // => 3
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*
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* _.reduce({ 'a': 1, 'b': 2 }, function(result, n, key) {
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* result[key] = n * 3;
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* return result;
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* }, {});
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* // => { 'a': 3, 'b': 6 } (iteration order is not guaranteed)
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*/
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function reduce(collection, iteratee, accumulator, thisArg) {
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var func = isArray(collection) ? arrayReduce : baseReduce;
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return func(collection, baseCallback(iteratee, thisArg, 4), accumulator, arguments.length < 3, baseEach);
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}
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module.exports = reduce;
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