proxy: 代理
扩展(增强)对象、方法(函数)一些功能
比如:
Vue
Vue.config.keyCodes.enter=65
Proxy作用: 比如vue中拦截
预警、上报、扩展功能、统计、增强对象等等
proxy是设计模式一种， 代理模式
语法:
new Proxy(target, handler);
let obj = new Proxy(被代理的对象,对代理的对象做什么操作)
handler:
{
set(){}, //设置的时候干的事情
get(){}, //获取干的事情
deleteProperty(){}, //删除
has(){} //问你有没有这个东西 'xxx' in obj
apply() //调用函数处理
.....
}
javascript
let obj = {
name:'Strive'
};
let newObj = new Proxy(obj,{//代理obj
get(target, property){//property 属性 get是获取信息
//console.log(target, property);
//TODO
console.log(`您访问了${property}属性`);
return target[property];//没有return返回值会都出现undefined
}
});
console.log(newObj.name);实现一个，访问一个对象身上属性，默认不存在的时候给了undefined，希望如果不存在错误(警告)信息：
javascript
let newObj = new Proxy(obj, {
get(target, property){
if(property in target){
return target[property];
}else{
//throw new ReferenceError(`${property}属性不在此对象上`);
console.warn(`${property}属性不在此对象上`);
return '^_^';//替换了出现的undefined
}
}
});DOM.div()
DOM.a();
DOM.ul()
例：
javascript
<script>
const DOM = new Proxy({},{
get(target, property){
//console.log(target, property);
//property就是DOM.xxx 里面的xxx
return function(attr={}, ...children){//json的内容，其他内容
//console.log(attr, children);
const el = document.createElement(property);
//添加属性
for(let key of Object.keys(attr)){
el.setAttribute(key, attr[key]);
}
//添加子元素
for(let child of children){
if(typeof child == 'string'){
child = document.createTextNode(child);//创建文本节点
}
el.appendChild(child);//添加
}
return el;
}
}
});
let oDiv = DOM.div({id:'div1',class:'aaa'},'我是div','呵呵呵');//json,内容，......
console.log(oDiv);
</script>
javascript
const DOM = new Proxy({},{
get(target, property){
//console.log(target, property);
//property DOM.xxx 里面的xxx
return function(attr={}, ...children){
//console.log(attr, children);
const el = document.createElement(property);
//添加属性
for(let key of Object.keys(attr)){
el.setAttribute(key, attr[key]);
}
//添加子元素
for(let child of children){
if(typeof child == 'string'){
child = document.createTextNode(child);
}
el.appendChild(child);
}
return el;
}
}
});
let oDiv = DOM.div(
{id:'div1',class:'aaa'},'我是div','呵呵呵',
DOM.a({href:'http://www.51mmr.net'}, '访问官网'),
DOM.ul({},
DOM.li({},'1111'),
DOM.li({},'2222'),
DOM.li({},'3333'),
DOM.li({},'4444')
)
);
window.onload=function(){
document.body.appendChild(oDiv);
};set(), 设置，拦截:
设置一个年龄，保证是整数，且范围不能超过200
javascript
let obj =new Proxy({},{
set(target, prop, value){
if(prop == 'age'){
if(!Number.isInteger(value)){
throw new TypeError(`年龄必须为整数`);
}
if(value>200){
throw new RangeError('年龄超标了，必须小于200岁');
}
}
target[prop]=value;
}
});
obj.a=123;
obj.name = 'Strive';
console.log(obj);
obj.age = 201;deleteProperty(): 删除，拦截:
javascript
let json = {
a:1,
b:2
};
let newJson = new Proxy(json, {
deleteProperty(target, property){
console.log(`您要删除${property}属性`);
//TODO
delete target[property];
}
});
delete newJson.a;
console.log(newJson);has(): 检测有没有
javascript
let newJson = new Proxy(json, {
deleteProperty(target, property){
console.log(`您要删除${property}属性`);
//TODO
delete target[property];
},
has(target, property){
console.log(`判断是否存在调用has方法`);
//TODO
return property in target;
}
});
console.log('a' in newJson);apply(target,context指向,args参数数组) :拦截方法
javascript
function fn(){
return '我是函数';
}
let newFn = new Proxy(fn, {
apply(){
return '函数么?';
}
});
console.log(newFn());Reflect: 反射
将Object.xxx 语言内部方法如：Object.defineProperty放到Reflect对象身上
通过Reflect对象身上直接拿到语言内部东西
比如：
'assign' in Object -> Reflect.has(Object, 'assign')
delete json.a -> Reflect.deleteProperty(json, 'a');
javascript
let json ={a:1, b:2};
/* delete json.a;
console.log(json); */
Reflect.deleteProperty(json, 'a');
console.log(json);Reflect.apply(调用的函数，this指向，参数数组);与fn.call() fn.apply() 作用类似
javascript
let res = Reflect.apply(Math.ceil,null, [9.8]);//变形式调用函数
console.log(res);
javascript
function show(...args){
console.log(this);
console.log(args);
}
//show(1,2,3,4);
//show.call('abc', 1,2,3,4);将this改变成abc
//show.apply('abcd',[1,2,3,4]);
Reflect.apply(show, 'aaaa', [1,2,3,4]);
javascript
function sum(a,b){
return a+b;
}
let newSum = new Proxy(sum, {
apply(target, context, args){
//console.log(target, context, args);
//console.log(...arguments);
return Reflect.apply(...arguments);
}
});
console.log(newSum(2,3))