网站建设在国外,如何在wordpress首页显示文章列表,建设银行网站收款怎么打明细,淮北专业网站建设一、代理
Proxy 用于修改某些操作的默认行为#xff0c;等同于在语言层面做出修改#xff0c;所以属于一种“元编程”#xff08;meta programming#xff09;#xff0c;即对编程语言进行编程。
Proxy 可以理解成#xff0c;在目标对象之前架设一层“拦截”#xff0…一、代理
Proxy 用于修改某些操作的默认行为等同于在语言层面做出修改所以属于一种“元编程”meta programming即对编程语言进行编程。
Proxy 可以理解成在目标对象之前架设一层“拦截”外界对该对象的访问都必须先通过这层拦截因此提供了一种机制可以对外界的访问进行过滤和改写。Proxy 这个词的原意是代理用在这里表示由它来“代理”某些操作可以译为“代理器”。
二、常用拦截方法 // ES5
let obj {}
let newVal
Object.defineProperty(obj, name, {get () {console.log(get)return newVal},set (val) {console.log(set)newVal val}
})
obj.name zz
console.log(obj.name )// ES6 proxy
let obj {}
let p new Proxy(obj, {})
p.name zzzzz
console.log(p, obj.name)// get
let arr [11,22,33]
arr new Proxy(arr, {get(target, key) {console.log(target, key)if (key in target) {return target[key]} else {return err}}
})
console.log(arr[5])// set
let arr []
arr new Proxy(arr, {set(target, key, val) {if (typeof val number) {target[key] valreturn true} else {return false}}
})
arr.push(1)
console.log(arr, arr[0], arr[1])// has
let range {min: 1,max: 5
}
range new Proxy(range, {has(target, key) {return key target.min key target.max}
})
console.log( 2 in range)
console.log( 6 in range)// ownKeys
let obj {name: zz,[Symbol(66)]: 66
}
Object.getOwnPropertyNames(obj)
Object.getOwnPropertySymbols(obj)
Object.keys(obj)
Reflect.ownKeys(obj)
let userInfo {name: zz,age: 25,_password: 123456
}
userInfo new Proxy(userInfo, {ownKeys(target) {return Object.keys(target).filter(key !key.startsWith(_))}
})
for (let key in userInfo) {console.log(key)
}
console.log(Object.keys(userInfo))// apply
let sum (...args) {let sum 0args.forEach(item {sum item})return sum
}
sum new Proxy(sum, {apply(target, ctx, args) {return target(...args) * 2}
})
console.log(sum(1,2))
console.log(sum.call(null, 1,2,3));// construct
let User class {constructor (name) {this.name name}
}
User new Proxy(User, {construct(target, args, newTarger) {return new target(...args)}
})
console.log(new User(zzz))//
let user {name: zz,age: 25,_password: 123456
}user new Proxy(user, {get(target, key) {if (key.startsWith(_)) {throw new Error(不可访问)} else {return target[key]}},set(target, key, val) {if (key.startsWith(_)) {throw new Error(不可访问)} else {target[key] valreturn true}},deleteProperty(target, key) {if (key.startsWith(_)) {throw new Error(不可删除)} else {delete target[key]return true}},ownKeys(target) {return Object.keys(target).filter(key !key.startsWith(_))},// apply
})
try {console.log(user._password)
} catch(e) {console.log(e.message)
}
console.log(user.name)
user.age 18
console.log(user)
for (let key in user) {console.log(key)
}
