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40 lines
1.1 KiB
40 lines
1.1 KiB
5 months ago
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var keys = require('./keys')
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/**
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* 接收一个函数作为累加器，数组中的每个值（从左到右）开始合并，最终为一个值。
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*
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* @param {Array} array 数组
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* @param {Function} callback 方法
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* @param {Object} initialValue 初始值
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* @return {Number}
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*/
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function reduce (array, callback, initialValue) {
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if (array) {
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var len, reduceMethod
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var index = 0
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var context = null
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var previous = initialValue
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var isInitialVal = arguments.length > 2
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var keyList = keys(array)
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if (array.length && array.reduce) {
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reduceMethod = function () {
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return callback.apply(context, arguments)
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}
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if (isInitialVal) {
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return array.reduce(reduceMethod, previous)
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}
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return array.reduce(reduceMethod)
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}
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if (isInitialVal) {
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index = 1
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previous = array[keyList[0]]
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}
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for (len = keyList.length; index < len; index++) {
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previous = callback.call(context, previous, array[keyList[index]], index, array)
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}
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return previous
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}
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}
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module.exports = reduce
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