详解VUE中的Proxy代理

let arr = [123,"ac","你好"]
arrPro = new Proxy(arr,{
    get(target,prop){
        // target 代表被代理的数组，也就是 [123,"ac","你好"]
        console.log(target)
        // prop 表示要访问的属性，也就是 0
        console.log(prop)
        return prop in target ? target[prop] : 'error'
    }
})
console.log(arrPro[0])

let arr = []
let arrPro = new Proxy(arr,{
    set(target,prop,val){
        if(typeof val === "number"){
            target[prop] = val
            return true
        }else{
            return false
        }
    }
}) 
arrPro.push(5) 
console.log(arr)  //[5]

let range = {
    start:1,
    end:5
}
range = new Proxy(range,{
    has(target,prop){
       return prop >= target.start && prop <= target.end
    }
})
console.log(2 in range) // true
console.log(6 in range) // false

let user = {
    name: 'ac',
    age: 12,
    _password: 'xxx'
}
 
user = new Proxy(user, {
    get(target, prop) {
        if (prop.startsWith('_')) {
            throw new Error('不可访问')
        } else {
            return target[prop]
        }
    },
    set(target, prop, val) {
        if (prop.startsWith('_')) {
            throw new Error('不可设置')
        } else {
            target[prop] = val
            return true
        }
    },
    deleteProperty(target, prop) {
        if (prop.startsWith('_')) {
            throw new Error('不可删除')
        } else {
            delete target[prop]
            return true
        }
    }
})
console.log(user.age)  //12
console.log(user._password)  //Error:不可访问
 
user.age = 22
console.log(user.age)  //22
 
delete user.age
console.log(user.age)  //undefined

let sum = (...args) =>{
    let num = 0
    args.forEach(item =>{
        num += item
    })
    return num
}
 
sum = new Proxy(sum,{
    apply(target,ctx,args){
        return target(...args) * 2
    }
})
console.log(sum(2,5)) //14
console.log(sum.call(null,2,5)) //14
console.log(sum.apply(null,[2,5]))  //14

let User = class {
    constructor(name){
        this.name = name
    }
}
User = new Proxy(User,{
    construct(target,args,newTarget){
        console.log("代理拦截")  //代理拦截
        return new target(...args)  //User {name: 'ac'}
    }
})
 
console.log(new User('ac'))