剖析vue3数据绑定原理 Proxy
2022/7/5 23:23:49
本文主要是介绍剖析vue3数据绑定原理 Proxy,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
//ES5 let obj = {} Object.defineProperty( obj, 'name', { get() { console.log('get'); return 'zxs' }, set() { console.log('set'); } })console.log(obj.name); //get zxs obj.name = 'es'
let obj1 = {} let newVal = '' Object.defineProperty(obj1, 'name', { get() { console.log('读取了属性'); return newVal; }, set(val) { console.log("设置了属性"); newVal = val; } })
console.log(obj1.name); obj1.name = 'es';
// ES6
let obj2 = {} let p = new Proxy(obj2, {}) //参数1:要包装(拦截)的对象 //参数2: 拦截方法钩子函数,类似于上面的get,set p.name = 'zxs'; console.log(obj2.name);
let arr = [7, 8, 9] arr = new Proxy(arr, { get(target, prop) { console.log('target: ' + target + 'prop: ' + prop); //target: 7,8,9 prop: 1 //target是要包装的整个对象,prop是带的参数 return prop in target ? target[prop] : 'error' } }) console.log(arr[1]); //target: 7,8,9 prop: 1 8 console.log(arr[10]); //target: 7,8,9 prop: 10 error
let dict = { 'hello': '你好', 'world': '世界' } dict = new Proxy(dict, { get(target, prop) { return prop in target ? target[prop] : prop } })
console.log(dict['world']); //世界 console.log(dict['zxs']); //zxs
let arr1 = [] arr1 = new Proxy(arr1, { set(target, prop, val) { if (typeof val === 'number') { console.log('target: ' + target + ' prop: ' + prop + ' val: ' + val); target[prop] = val return true } else { return false } } })
arr1.push(5); //target: prop: 0 val: 5 arr1.push(6) //target: 5 prop: 1 val: 6 console.log(arr1[0], arr1[1], arr1.length); //target: 5,6 prop: length val: 2 //5 6 2
// has 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 userinfo = { username: 'zxs', age: 100, _pwd: '1234' //不想让外界访问到_pwd }
userinfo = new Proxy(userinfo, { ownKeys(target) { return Object.keys(target).filter(key => !key.startsWith('_')); } })
for (let i in userinfo) { console.log(i); //username //age }
console.log(Object.keys(userinfo)); //['username', 'age']
let user = { username: 'zxs', age: 100, _pwd: '12345' //不想让外界访问到_pwd,删除_pwd等等所有操作 }
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('不可访问') } 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 } }, ownKeys(target) { return Object.keys(target).filter(key => !key.startsWith('_')) } })
console.log(user); //['username', 'age'] console.log(user._pwd); //Error:不可访问 user.age = 18; console.log(user.age = 18);
// try { // user._pwd = 'xxx' // } catch (e) { // console.log(e.message); //不可访问 // }
// try { // delete user._pwd // } catch (e) { // console.log(e.message); //不可删除 // }
for (let key in user) { console.log(key); //username //age }
// apply
//未知参数求和 let sum = (...args) => { let num = 0; args.forEach(item => { num += item }) return num; } sum = new Proxy(sum, { apply(target, ctx, args) { //ctx :目标对象的上下文对象(this) return target(...args) * 2 //将求和函数结果*2 } }) console.log(sum(1, 1, 1 ));//6 console.log(sum.call(null, 1, 1, 1)); //6 console.log(sum.apply(null,[1,1,1]));//6
// construct let user1=class{ constructor(name){ this.name=name } } user1 = new Proxy(user1, { //拦截 new一个对象 construct(target, args,newTarget){ return new target(...args) } })
console.log(new user1('zxs')); //user1 {name: 'zxs'}
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