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110 lines
3.3 KiB
JavaScript
110 lines
3.3 KiB
JavaScript
/**
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* lodash (Custom Build) <https://lodash.com/>
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* Build: `lodash modularize exports="npm" -o ./`
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* Copyright jQuery Foundation and other contributors <https://jquery.org/>
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* Released under MIT license <https://lodash.com/license>
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* Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
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* Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
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*/
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var baseEach = require('lodash._baseeach'),
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baseIteratee = require('lodash._baseiteratee'),
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baseReduce = require('lodash._basereduce');
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/**
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* A specialized version of `_.reduce` for arrays without support for
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* iteratee shorthands.
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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} [initAccum] Specify using the first element of `array` as
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* 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, initAccum) {
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var index = -1,
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length = array.length;
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if (initAccum && 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` 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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/**
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* Checks if `value` is classified as an `Array` object.
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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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* @type {Function}
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* @category Lang
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* @param {*} value The value to check.
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* @returns {boolean} Returns `true` if `value` is correctly classified,
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* else `false`.
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* @example
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*
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* _.isArray([1, 2, 3]);
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* // => true
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*
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* _.isArray(document.body.children);
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* // => false
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*
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* _.isArray('abc');
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* // => false
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*
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* _.isArray(_.noop);
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* // => false
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*/
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var isArray = Array.isArray;
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module.exports = reduce;
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