发起看这片文章时能够点击音乐🎵,来个单曲轮回,美滋滋
先拿call开刀
作用:call和apply都是替代函数内毛病的this
var a = {
value:1
}
var b = function(){
console.log(this.value) // 假如不对this举行绑定实行bar() 会返回undefined
}
b.call(a) //1
去除烦琐的解说,一步到位本身模仿call的用法写一个函数,到达雷同目标
Function.prototype.myCall = function(context){
var context = context || window; //当没传入值时刻,就是指全局window
context.fn = this; //把挪用myCall前的要领缓存下来
var args = [...arguments].slice(1);//运用...打散传入值,并去除第一要领,获得一个数组
var result = context.fn(...args);//把数组打散,把dinging 18传入b要领中
delete context.fn; //删除
return result
}
var a = {
value:1
}
var b = function(name,age){
console.log(this.value)
console.log(name)
console.log(age)
}
b.myCall(a,"dingding",18)
apply
apply的要领和 call 要领的完成相似,只不过是假如有参数,以数组情势举行通报
apply这个API日常平凡运用的场景,代码以下:
var a = {
value:1
}
var b = function(name,age){
console.log(this.value)
console.log(name)
console.log(age)
}
b.apply(a,["dingding",18])
直接上模仿apply功用代码
Function.prototype.myApply = function(context){
var context = context || window;
context.fn = this;
var result;
if(arguments[1]){
result = context.fn(...arguments[1])
}else{
result = context.fn()
}
delete context.fn
return result
}
var a = {
value:1
}
var b = function(name,age){
console.log(this.value)
console.log(name)
console.log(age)
}
b.myApply(a,["dingding",18])