es5实现mapfilter

// ES5循环循环实现filter

const selfFilter = function (fn, context) { let arr = Array.prototype.slice.call(this) let filteredArr = [] for (let i = 0; i < arr.length; i++) { if(!arr.hasOwnProperty(i)) continue; fn.call(context, arr[i], i, this) && filteredArr.push(arr[i]) } return filteredArr }

 

 

 

// ES5循环实现map

const selfMap = function (fn, context) { let arr = Array.prototype.slice.call(this) let mappedArr = [] for (let i = 0; i < arr.length; i++) { // 判断稀疏数组的情况 if (!arr.hasOwnProperty(i)) continue; mappedArr.push(fn.call(context, arr[i], i, this)) } return mappedArr }

 

 

// reduce实现map

const selfMap2 = function (fn, context) { let arr = Array.prototype.slice.call(this) return arr.reduce((pre, cur, index) => { return [...pre, fn.call(context, cur, index, this)] }, []) }

 

转载于:https://www.cnblogs.com/qdcnbj/p/11186832.html