[JavaScript知识库]JavaScript中的面向对象thiscall applybind

this

1. 全局模式和函数下，指的对象是this。
2. 在 ‘use strict’ 下是undefined

function show(){
	console.log(this);	
}
show() //window
------------------------------------------------------------
'user strict'
function show(){
	console.log(this);	
}
show() //undefined

3. 对象this -> {}

'user strict'
var teacer = {
	name:'leo',
	showName:function(){
		function testThis(){
			console.log(this.name);
		}
		testThis();
}
teacer.showName(); //undefined
                   //因为此时的this对应的是window。window没有name因此返回undefined
-------------------------------------------------------
name = 'jesslyn';
var teacer = {
	name:'leo',
	showName:function(){
		function testThis(){
			console.log(this.name);
		}
		testThis();
}
teacer.showName(); //jesslyn
				   //因为此时的闭包里面的this指的是window,因此在window下找到name

这个时候如果要打印leo怎么办呢？以下提供了三种方法：
a. let接一下
b. 箭头函数
c. bind apply call

name = 'jesslyn';
var teacer = {
	name:'leo',
	showName:function(){
		let that = this; //矫正
		function testThis(){
			console.log(this.name);
		}
		testThis();
}
teacer.showName();
----------------------------------------------------
name = 'jesslyn';
var teacer = {
	name:'leo',
	showName:function(){
		function testThis(){
			console.log(this.name);
		}.bind(this);  //矫正，绑定teacer
		testThis();
}
teacer.showName();
---------------------------------------------------------
function show(a,b){
	console.log(this,12,5)
}
show.call(66666.12,5) //{666666} 12 5 
					  //.call(矫正this，参数1，参数2）
show.apply(66666,[12,5]) //{666666} 12 5 
						//.aplly(this,[参数1，参数2]),通常不用写this,写null即可
						

参考视频
https://www.bilibili.com/video/BV15x411f7xe?p=14