SOURCE

// 一、Object.defineProperty()
let count =2 
let double = count * 2


let obj = {
    count:2
}


function getDouble(val) {
    return val*2
}


Object.defineProperty(obj,'count',{
    get() {
        return count
    },
    set(val) {
        console.log(val) // 3
       double = getDouble(val)
    }
})

console.log(double) // 4

obj.count = 3 

console.log(double) // 6


console.log('---------------------')

// 二、Proxy
let target = {} ;

proxy = new Proxy(target,{
    // get拦截器
    get(target,key) {
        console.log(target,key) // {} age
        return 30
    },
    // set拦截器
    set(target,key,value) {
       console.log(target,key,value)  // {} name iu
       target[key] = value
    },
    deleteProperty(target,key) {
        console.log(target,key) // {'name':'iu' }  name
       return delete target[key]
    }
})
proxy.age 
proxy.name = 'iu'
console.log(target.name) // iu

delete proxy.name
console.log(target.name) // undefined

console.log('---------------')

// 三、Object get/set
let _val  = 6
let double1 = getDouble(_val)
let count1 = {
    get value() {
        return _val
    },
    set value(val) {
        console.log(val)
        _val = val
        double1 = getDouble(val)
    } 
}

count1.value = 2
console.log(double1)