本文共 2646 字,大约阅读时间需要 8 分钟。
forEach
Array.prototype.myForEach = function(func) { var len = this.length; for(var i = 0; i < len; i++) { func(this[i], i); }}复制代码
filter
Array.prototype.myFilter = function(func) { var len = this.length, newArr = []; for(var i = 0; i < len; i++) { if(func(this[i], i)) { newArr.push(this[i]); } } return newArr;}复制代码
map
Array.prototype.myMap = function(func) { var len = this.length, newArr = []; for(var i = 0; i < len; i++) { newArr.push(func(this[i], i)); } return newArr;}复制代码
// 深度克隆function deepClone(target, option) { if(option !== null) { for(var prop in option) { var src = target[prop], copy = option[prop]; if(typeof(copy) === 'object') { if(Object.prototype.toString(copy) === '[object Array]') { src = []; }else { src = {}; } target[prop] = deepClone(src, copy); }else { target[prop] = copy; } } } return target;}Array.prototype.myMap = function(func) { var len = this.length, newArr = []; for(var i = 0; i < len; i++) { if(this[i] && Object.prototype.toString.call(this[i]) === '[object Object]') { var newObj = {}; deepClone(newObj, this[i]); newArr.push(func(newObj, i)); }else if(this[i] && Object.prototype.toString.call(this[i]) === '[object Array]') { var Arr = []; deepClone(newArr, this[i]); newArr.push(func(Arr, i)); }else { newArr.push(func(this[i], i)); } } return newArr;}复制代码
reduce
作用: 迭代数组,从左向右,累加器(效率高)。
源码实现
Array.prototype.myMap = function(func, init) { var k = 0, prev = init, len = this.length; if(init === undefined) { prev = this[0]; k = 1; } for(k; k < len; k++) { prev = func(prev, this[k], k); } return prev;};复制代码
reduce
Array.prototype.myReduceRight = function(func, init) { var prev = init, len = this.length, k = len - 1; if(init === undefined) { prev = this[k]; k = len - 2; } for(k; k >= 0; k --) { prev = func(prev, this[k], k); } return prev;}