SOURCE

let targetObj = {
    age: 18,
}

function Observer(oldval,newval){
    console.info('name属性的值从 '+ oldval +' 改变为 ' + newval);
}

Object.defineProperty(targetObj, 'name', {
    enumerable: true,
    configurable: true,
    get: function() {
        return name
    },
    set: function(val) {
        Observer(name, val)
        name = val 
    }
})

targetObj.name = 'zhang'
targetObj.name = 'yang'

function Observer1(oldval,newval){
    console.info('name属性的值从 '+ oldval +' 改变为 ' + newval);
}

class TargetObj {
    constructor(name, age){
        this.name = name
        this.age = age
    }
    set name (val) {
        Observer1(name, val)
        name = val
    }
}

let tar = new TargetObj('yi', 18)
tar.name = 'china'