<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<button>按钮</button>
<script>
// this指向问题
var that;
var _that;
class Fa {
//constructor 里面的this指向的是 创建的实例对象(ff)
constructor(x, y){
that = this;
this.x = x;
this.y = y;
this.btn = document.querySelector('button');
this.btn.onclick = this.sing;
}
sing(){
// this指向的是 btn这个按钮 因为这个按钮调用了这个函数
console.log("11111111111");
console.log(that.x);
// that 里面存储的是constructor里面的this
// console.log(this.x);
}
sum(){
//这个sum 里面的this指向的是实例对象ff 因为ff调用了这个函数(this指向sum方法的调用者ff)
_that = this;
console.log(this.x + this.y);
}
}
var ff = new Fa(1,2);
console.log(that === ff); // true
// console.log(ff);
// // Fa {x: 1, y: 2}
ff.sum();
console.log(_that === ff); // true
</script>
</body>
</html>