创建一个简单的Proxy
let target = {}
let proxy = new Proxy(target, {})
proxy.name = 'proxy'
console.log(proxy.name) // proxy
console.log(target.name) // proxy
target.name = 'target'
console.log(proxy.name) // target
console.log(target.name) // target这个实例将"proxy"赋值给proxy.name属性时会在目标上创建name,代理只是简单的将操作转发给目标，他不会储存这个属性。相当于proxy.name和target.name引用的都是target.name的值。
使用set陷阱验证属性
set陷阱接收四个参数：
1.trapTarget：用于接收属性（代理的目标）的对象
2.key：要写入的属性键（字符串或者symbol）
3.value：被写入的属性值
4.receiver：操作发生的对象（通常是代理）
let target = {
name: "target"
}
let proxy = new Proxy(target, {
set(trapTarget, key, value, receiver) {
if (!trapTarget.hasOwnProperty(key)) {
if (isNaN(value)) {
throw new TypeError("属性必须时数字")
}
}
return Reflect.set(trapTarget, key, value, receiver)
}
})
proxy.count = 1
console.log(proxy.count) //1
console.log(target.count) //1
proxy.name = "proxy"
console.log(proxy.name) //proxy
console.log(target.name) //proxy
proxy.other = "other" // 这里会报错因为不数字这个实例每次在外面改变proxy的值时就会出发set函数。
用get陷阱验证对象结构
get接收3个参数
1.trapTarget：用于接收属性（代理的目标）的对象
2.key：要写入的属性键（字符串或者symbol）
3.receiver：操作发生的对象（通常是代理）
let proxy = new Proxy({}, {
get(trapTarget, key, receiver) {
if (!(key in receiver)) {
throw new TypeError("属性" + key + "不存在")
}
return Reflect.get(trapTarget, key, receiver)
}
})
proxy.name = "proxy"
console.log(proxy.name) //proxy
console.log(proxy.age) // 属性不存在会抛出错误当我们访问proxy创建的对象属性时就会触发get方法
使用has陷阱因此已有属性
has接收2个参数：
1.trapTarget：用于接收属性（代理的目标）的对象
2.key：要写入的属性键（字符串或者symbol）
let target = {
name: "target",
value: 42
}
let proxy = new Proxy(target, {
has(trapTarget, key) {
if (key === 'value') {
return false
} else {
return Reflect.has(trapTarget, key)
}
}
})
console.log("value" in proxy) // false
console.log("name" in proxy) // true
console.log("toString" in proxy) // true用deleteProperty陷阱防止删除属性
deleteProperty接收2个参数：
1.trapTarget：用于接收属性（代理的目标）的对象
2.key：要写入的属性键（字符串或者symbol）
let target = {
name: "target",
value: 42
}
let proxy = new Proxy(traget, {
deleteProperty(trapTarget, key) {
if (key === "value") {
return false
} else {
return Reflect.deleteProperty(trapTarget, key)
}
}
})
console.log("value" in proxy) // true
let result1 = delete proxy.value
console.log(result1) // false
console.log("value" in proxy) // true
console.log("name" in proxy) // true
let result2 = delete proxy.name
console.log(result2) // true
console.log("name" in proxy) // false当外部要删除proxy的属性就会触发deleteProperty函数
原型代理陷阱(setProptotypeOf,getPrototypeOf)
setProptotypeOf接收2个参数
1.trapTarget：用于接收属性（代理的目标）的对象
2.proto：作为原型使用的对象
let target = {}
let proxy = new Proxy(target, {
// 访问时调用
getPrototypeOf(trapTarget) {
return null
},
// 改变时调用
setPrototypeOf(trapTarget, proto) {
return false
}
})
let targetProto = Object.getPrototypeOf(target)
let proxyProto = Object.getPrototypeOf(proxy)
console.log(targetProto === Object.prototype) //true
console.log(proxyProto === Object.prototype) // false
console.log(proxyProto) // null
Object.setPrototypeOf(target, {}) // 成功
Object.setPrototypeOf(proxy, {}) // 抛出错误如果正常实现
let target = {}
let proxy = new Proxy(target, {
// 访问时调用
getPrototypeOf(trapTarget) {
return Reflect.getPrototypeOf(trapTarget)
},
// 改变时调用
setPrototypeOf(trapTarget, proto) {
return Reflect.setPrototypeOf(trapTarget, proto)
}
})
let targetProto = Object.getPrototypeOf(target)
let proxyProto = Object.getPrototypeOf(proxy)
console.log(targetProto === Object.prototype) //true
console.log(proxyProto === Object.prototype) // true
Object.setPrototypeOf(target, {}) // 成功
Object.setPrototypeOf(proxy, {}) // 成功属性描述符陷阱
defineProperty接收三个参数：
1.trapTarget：用于接收属性（代理的目标）的对象
2.key：要写入的属性键（字符串或者symbol）
3.descriptor：属性的描述对象
let proxy = new Proxy({}, {
defineProperty(trapTarget, key, descriptor) { // descriptor 只能接收enumerable, configurable, value, writeable, get, set
if (typeof key === "symbol") {
return false
}
return Reflect.defineProperty(trapTarget, key, descriptor)
},
getOwnPropertyDescriptor(trapTarget, key) {
return Reflect.getOwnPropertyDescriptor(trapTarget, key)
}
})
Object.defineProperty(proxy, "name", {
value: "proxy"
})
console.log(proxy.name) //proxy
let nameSymbol = Symbol("name")
Object.defineProperty(proxy, nameSymbol, {
value: "proxy"
})在外部调用defineProperty | getOwnPropertyDescriptor时会触发内部definenProperty | getOwnPropertyDescriptor方法。
ownKeys陷阱
ownKeys陷阱会拦截外部的Object.keys()，Object.getOwnPropertyName(),Object.getOwnPropertySymbols()和Object.assign()四个方法
let proxy = new Proxy({}, {
ownKeys(trapTarget) {
return Reflect.ownKeys(trapTarget).filter(key => {
return typeof key !== "string" || key[0] !== '_'
})
}
})
let nameSymbol = Symbol("name")
proxy.name = "proxy"
proxy._name = "private"
proxy[nameSymbol] = "symbol"
let names = Object.getOwnPropertyNames(proxy),
keys = Object.keys(proxy),
symbols = Object.getOwnPropertySymbols(proxy)
console.log(names.length) // 1
console.log(names) // name
console.log(keys.length) //1
console.log(keys[0]) // name
console.log(symbols.length) //1
console.log(symbols[0]) // symbol(name)更多编程相关知识，请访问：编程入门！！
