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<html lang="en">
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<meta charset="UTF-8">
<title>Document</title>
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<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>
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