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易知道(ezd.cc)的更多内容!
