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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<title>Learn Proxy</title>
<style>
.pre {
background-color: #eee;
}
.li {
line-height: 2;
}
</style>
</head>
<body style="padding: 0 72px 72px 72px">
<h1>Proxy</h1>
<h2>语法</h2>
<pre class="pre">
var proxy = new Proxy(target, handler);
</pre>
<h3>例子1</h3>
<pre class="pre">
var obj = new Proxy(
{},
{
get: function(target, key, receiver) {
console.log(`getting ${key}!`);
return Reflect.get(target, key, receiver);
},
set: function(target, key, value, receiver) {
console.log(`setting ${key}!`);
return Reflect.set(target, key, value, receiver);
}
}
);
</pre>
<h3>例子2</h3>
<pre class="pre">
var handler = {
get: function(target, name) {
if (name === "prototype") {
return Object.prototype;
}
return "Hello, " + name;
},
apply: function(target, thisBinding, args) {
return args[0];
},
construct: function(target, args) {
return { value: args[1] };
}
};
var fproxy = new Proxy(function(x, y) {
return x + y;
}, handler);
</pre>
<script>
var obj = new Proxy(
{},
{
get: function (target, key, receiver) {
console.log(`getting ${key}!`);
return Reflect.get(target, key, receiver);
},
set: function (target, key, value, receiver) {
console.log(`setting ${key}!`);
console.log('receiver==', receiver)
return Reflect.set(target, key, value, receiver);
}
}
);
obj.count = 1
console.log('obj =====', obj.count)
// obj.count = 1;
var handler = {
get: function (target, name) {
if (name === "prototype") {
return 'test'
}
return "Hello, " + name;
},
apply: function (target, thisBinding, args) {
return args[0];
},
construct: function (target, args) {
return { value: args[1] };
}
};
var fproxy = new Proxy(function (x, y) {
return x + y;
}, handler);
console.log('fproxy =====', fproxy)
fproxy(1, 2); // 1
new fproxy(1, 2); // {value: 2}
fproxy.prototype === 'test'; // true
fproxy.foo === "Hello, foo"; // true
</script>
<h2>应用场景</h2>
<h3>1 缓存代理</h3>
<pre class="pre">
const getFib = (number) => {
if (number <= 2) {
return 1;
} else {
return getFib(number - 1) + getFib(number - 2);
}
}
</pre>
<script>
const getFib = number => {
if (number <= 2) {
return 1;
} else {
return getFib(number - 1) + getFib(number - 2);
}
};
</script>
<pre class="pre">
const getCacheProxy = (fn, cache = new Map()) => {
return new Proxy(fn, {
apply(target, context, args) {
const argsString = args.join(' ');
if (cache.has(argsString)) {
// 如果有缓存,直接返回缓存数据
console.log(`输出${args}的缓存结果: ${cache.get(argsString)}`);
return cache.get(argsString);
}
const result = fn(...args);
cache.set(argsString, result);
return result;
}
})
}
const getFibProxy = getCacheProxy(getFib);
</pre>
<script>
const getCacheProxy = (fn, cache = new Map()) => {
return new Proxy(fn, {
apply(target, context, args) {
const argsString = args.join(" ");
if (cache.has(argsString)) {
// 如果有缓存,直接返回缓存数据
console.log(
`输出${args}的缓存结果: ${cache.get(
argsString
)}`
);
return cache.get(argsString);
}
const result = fn(...args);
cache.set(argsString, result);
return result;
}
});
};
const getFibProxy = getCacheProxy(getFib);
</script>
<h3>2 验证代理</h3>
<pre class="pre">
// 表单对象
const userForm = {
account: "",
password: ""
};
// 验证方法
const validators = {
account(value) {
// account 只允许为中文
const re = /^[\u4e00-\u9fa5]+$/;
return {
valid: re.test(value),
error: '"account" is only allowed to be Chinese'
};
},
password(value) {
// password 的长度应该大于6个字符
return {
valid: value.length >= 6,
error: '"password "should more than 6 character'
};
}
};
</pre>
<pre class="pre">
const getValidateProxy = (target, validators) => {
return new Proxy(target, {
_validators: validators,
set(target, prop, value) {
if (value === "") {
console.error(
`"${prop}" is not allowed to be empty`
);
return (target[prop] = false);
}
const validResult = this._validators[prop](value);
if (validResult.valid) {
return Reflect.set(target, prop, value);
} else {
console.error(`${validResult.error}`);
return (target[prop] = false);
}
}
});
};
const userFormProxy = getValidateProxy(userForm, validators);
</pre>
<script>
// 表单对象
const userForm = {
account: "",
password: ""
};
// 验证方法
const validators = {
account(value) {
// account 只允许为中文
const re = /^[\u4e00-\u9fa5]+$/;
return {
valid: re.test(value),
error: '"account" is only allowed to be Chinese'
};
},
password(value) {
// password 的长度应该大于6个字符
return {
valid: value.length >= 6,
error: '"password "should more than 6 character'
};
}
};
const getValidateProxy = (target, validators) => {
return new Proxy(target, {
_validators: validators,
set(target, prop, value) {
if (value === "") {
console.error(
`"${prop}" is not allowed to be empty`
);
return (target[prop] = false);
}
const validResult = this._validators[prop](value);
if (validResult.valid) {
return Reflect.set(target, prop, value);
} else {
console.error(`${validResult.error}`);
return (target[prop] = false);
}
}
});
};
const userFormProxy = getValidateProxy(userForm, validators);
</script>
<h3>3 实现私有属性</h3>
<pre class="pre">
function getPrivateProps(obj, filterFunc) {
return new Proxy(obj, {
get(obj, prop) {
if (!filterFunc(prop)) {
let value = Reflect.get(obj, prop);
// 如果是方法, 将this指向修改原对象
if (typeof value === "function") {
value = value.bind(obj);
}
return value;
}
},
set(obj, prop, value) {
if (filterFunc(prop)) {
throw new TypeError(`Can't set property "${prop}"`);
}
return Reflect.set(obj, prop, value);
},
has(obj, prop) {
return filterFunc(prop)
? false
: Reflect.has(obj, prop);
},
ownKeys(obj) {
return Reflect.ownKeys(obj).filter(
prop => !filterFunc(prop)
);
},
getOwnPropertyDescriptor(obj, prop) {
return filterFunc(prop)
? undefined
: Reflect.getOwnPropertyDescriptor(obj, prop);
}
});
}
function propFilter(prop) {
return prop.indexOf("_") === 0;
}
const myObj = {
public: "hello",
_private: "secret",
method: function() {
console.log(this._private);
}
},
myProxy = getPrivateProps(myObj, propFilter);
console.log(JSON.stringify(myProxy));
console.log(myProxy._private);
console.log("_private" in myProxy);
console.log(Object.keys(myProxy));
for (let prop in myProxy) {
console.log(prop);
}
myProxy._private = 1;
</pre>
<script>
function getPrivateProps(obj, filterFunc) {
return new Proxy(obj, {
get(obj, prop) {
if (!filterFunc(prop)) {
let value = Reflect.get(obj, prop);
// 如果是方法, 将this指向修改原对象
if (typeof value === "function") {
value = value.bind(obj);
}
return value;
}
},
set(obj, prop, value) {
if (filterFunc(prop)) {
throw new TypeError(`Can't set property "${prop}"`);
}
return Reflect.set(obj, prop, value);
},
has(obj, prop) {
return filterFunc(prop)
? false
: Reflect.has(obj, prop);
},
ownKeys(obj) {
return Reflect.ownKeys(obj).filter(
prop => !filterFunc(prop)
);
},
getOwnPropertyDescriptor(obj, prop) {
return filterFunc(prop)
? undefined
: Reflect.getOwnPropertyDescriptor(obj, prop);
}
});
}
function propFilter(prop) {
return prop.indexOf("_") === 0;
}
const myObj = {
public: "hello",
_private: "secret",
method: function () {
console.log(this._private);
}
},
myProxy = getPrivateProps(myObj, propFilter);
// console.log(JSON.stringify(myProxy)); // {"public":"hello"}
// console.log(myProxy._private); // undefined
// console.log("_private" in myProxy); // false
// console.log(Object.keys(myProxy)); // ["public", "method"]
// for (let prop in myProxy) {
// console.log(prop);
// } // public method
// myProxy._private = 1; // Uncaught TypeError: Can't set property "_private"
</script>
<h3>4 函数节流</h3>
<button>函数节流</button>
<pre class="pre">
const createThrottleProxy = (fn, rate) => {
let lastClick = Date.now() - rate;
return new Proxy(fn, {
apply(target, context, args) {
if (Date.now() - lastClick >= rate) {
fn(args);
lastClick = Date.now();
}
}
});
};
const handler2 = () => console.log("Do something...");
const handlerProxy = createThrottleProxy(handler2, 1000);
document.querySelector('button').addEventListener("click", handlerProxy);
</pre>
<script>
const createThrottleProxy = (fn, rate) => {
let lastClick = Date.now() - rate;
return new Proxy(fn, {
apply(target, context, args) {
if (Date.now() - lastClick >= rate) {
fn(args);
lastClick = Date.now();
}
}
});
};
const handler2 = () => console.log(Date.now(), "Do something...");
const handlerProxy = createThrottleProxy(handler2, 1000);
document
.querySelector("button")
.addEventListener("click", handlerProxy);
</script>
<!-- <h3>图片懒加载</h3>
<pre class="pre"></pre>
<script>
// const img = new Image();
// img.src = "/Users/wangliang/Desktop/loading.gif";
// document.body.appendChild(img);
const createImgProxy = (img, loadingImg, realImg) => {
let hasLoaded = false;
const virtualImg = new Image();
virtualImg.src = realImg;
virtualImg.onload = () => {
Reflect.set(img, "src", realImg);
hasLoaded = true;
};
return new Proxy(img, {
get(obj, prop) {
if (prop === "src" && !hasLoaded) {
console.log('xxxx')
return loadingImg;
}
return obj[prop];
}
});
};
const img = new Image();
// img.src = "/Users/wangliang/Desktop/loading.gif";
// const img = new Image();
const imgProxy = createImgProxy(
img,
"/Users/wangliang/Desktop/loading.gif",
"https://assets.souche.com/assets/sccimg//66af72b7cf46609b757f7e4551b421aa_02.png"
);
console.log(imgProxy)
document.body.appendChild(imgProxy);
</script> -->
<h3>5 异步队列</h3>
<pre class="pre">
const callback = () => console.log("Do something...");
const asyncFunc = cb => {
setTimeout(cb, 1000);
};
asyncFunc(callback);
asyncFunc(callback);
asyncFunc(callback);
const createAsyncQueueProxy = asyncFunc => {
let promise = null;
return new Proxy(asyncFunc, {
apply(target, context, [cb, ...args]) {
promise = Promise.resolve(promise).then(
() =>
new Promise(resolve => {
Reflect.apply(asyncFunc, this, [
() => {
cb();
resolve();
},
...args
]);
})
);
}
});
};
const timeoutProxy = createAsyncQueueProxy(asynFunc);
timeoutProxy(callback);
timeoutProxy(callback);
timeoutProxy(callback);
</pre>
<script>
const callback = () => console.log("Do something...");
const asyncFunc = cb => {
setTimeout(cb, 1000);
};
const createAsyncQueueProxy = asyncFunc => {
let promise = null;
return new Proxy(asyncFunc, {
apply(target, context, [cb, ...args]) {
promise = Promise.resolve(promise).then(
() =>
new Promise(resolve => {
Reflect.apply(asyncFunc, this, [
() => {
cb();
resolve();
},
...args
]);
})
);
}
});
};
const timeoutProxy = createAsyncQueueProxy(asyncFunc);
</script>
</body>
</html>