javascript - 在原型上实现 filter 方法？

Question

应该怎么修改代码呀？才能运行过去

解决问题

Answer 1

把接收的形参补充上去就可以了，图上的测试用例试了没问题的

Array.prototype.myFilter = function (callbak) {  const newArr = [];  this.forEach((e, index, array) => {    if (callbak(e, index, array)) {      newArr.push(e);    }  });  return newArr;};

Answer 2

- this.forEach(function(x) {+ this.forEach(function(x, index) {-     if (callback(x) == true) {+     if (callback(x, index, this)) {            newArray.push(x);      }  })

Answer 3

Array.prototype._filter = function(fn) {    if (typeof fn !== "function") {        throw Error('参数必须是一个函数');    }    const res = [];    for (let i = 0, len = this.length; i < len; i++) {        fn(this[i]) && res.push(this[i]);    }    return res;}