let data = { a: 100 };
let p = new 

let json = { _a: 10 };
Object.defineProperty(json, "a", {
get() 

class A{
    constructor(){
        this.username = 'vvheat';
    }
    show(){
        console.log(this.username);
        console.log(this.age);        //父类A根本没有age这个属性
    }

.btn-trigger{
  position:relative;
  &::before{
    content:'';
    position:absolute;
    left:-10px;