1.检查当前调用的是否为函数
2.如果当前没有传入指向的this,则赋值为window
3.将fn指向当前调用的函数
4.获取传入的参数
5.将参数传入fn进行调用
6.将对象上的fn删除
7.返回结果
- //普通call的实现
- function hello(){
- console.log('hello 我是'+this.name);
- };
- let person = {
- name:'krys'
- };
- var name = 'liang';//只有var的变量属于window
- hello();// 'hello 我是liang'
- hello.call(person);//'hello 我是krys'
- hello.call();//'hello 我是liang'
- let person2 = {
- name:'lwl'
- }
- Function.prototype.mycall = function(context){
- //不传入参数的时候,默认为window
- if(typeof this !== "function"){
- throw new TypeError('Error');
- }
- context = context || window;
- context.fn = this;//fn就是上面的hello方法
- const args = [...arguments].slice(1);//第一个参数不要
- const result = context.fn(...args);//把剩下的其他参数传给hello
- delete context.fn;
- return result;
- }
- hello.mycall(person2);
- function getParams(){
- console.log('我是',this.name,'获取一些参数',...arguments);
- }
- let person3 = {
- name:'hhh'
- };
- getParams.apply(person3,['hello','world'])
- Function.prototype.myApply = function(context){
- if(typeof this !== "function"){
- throw new TypeError()
- }
- context = context || window;
- context.fn = this;
- let result;
- if(arguments[1]){
- //如果有传入参数数组
- console.log(arguments[1])
- result = context.fn(...arguments[1]);
- }else{
- result = context.fn();
- }
- delete context.fn;
- return result;
- }
- getParams.myApply({name:'llll'},['jjj','kkkk','llll']);
- function getParams(){
- console.log('我是',this.name,'获取一些参数',...arguments);
- }
- let person3 = {
- name:'hhh'
- };
- let person4 = {
- name:'tttt'
- };
- getParams.bind(person3,'hello','world')
- getParams.bind(person4,'hello','world')('jjj','kkk');
- Function.prototype.myBind = function(context){
- if(typeof this !== "function"){
- throw new TypeError()
- }
- context = context || window;
- const _that = this;
- const args = [...arguments].slice(1);
- return function F(){
- if(this instanceof F){
- return new _that(...args,...arguments);//这里的arguments是上面的jjj kkk
- }
- return _that.apply(context,args.concat(...arguments));//这里的arguments是上面的jjj kkk
- }
- }
- getParams.myBind({name:'llll'},'jjj','kkkk','llll')('hhhhllll');
总结
本篇文章就到这里了,希望能够给你带来帮助,也希望您能够多多关注w3xue的更多内容!