40 lines
1.4 KiB
Java
40 lines
1.4 KiB
Java
var isArray = require('../base/isArray')
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/**
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* 浅复制数组的一部分到同一数组中的另一个位置,数组大小不变
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*
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* @param {Array} array 数组
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* @param {Number} target 从该位置开始替换数据
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* @param {Number} start 从该位置开始读取数据，默认为 0 。如果为负值，表示倒数
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* @param {Number} end 到该位置前停止读取数据，默认等于数组长度。如果为负值，表示倒数
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* @return {Array}
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*/
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function copyWithin (array, target, start, end) {
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if (isArray(array) && array.copyWithin) {
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return array.copyWithin(target, start, end)
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}
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var replaceIndex, replaceArray
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var targetIndex = target >> 0
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var startIndex = start >> 0
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var len = array.length
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var endIndex = arguments.length > 3 ? end >> 0 : len
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if (targetIndex < len) {
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targetIndex = targetIndex >= 0 ? targetIndex : len + targetIndex
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if (targetIndex >= 0) {
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startIndex = startIndex >= 0 ? startIndex : len + startIndex
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endIndex = endIndex >= 0 ? endIndex : len + endIndex
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if (startIndex < endIndex) {
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for (replaceIndex = 0, replaceArray = array.slice(startIndex, endIndex); targetIndex < len; targetIndex++) {
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if (replaceArray.length <= replaceIndex) {
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break
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}
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array[targetIndex] = replaceArray[replaceIndex++]
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}
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}
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}
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}
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return array
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}
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module.exports = copyWithin
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