继承
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1.什么是继承
比如：充值会员分为普通会员和vip会员，那么普通会员有的vip会员肯定有，vip会员有的普通会员不一定有，普通会员可以看出一个父级，vip会员可以看出一个子级，父级有的子级一定有，子级有的父级不一定有
2.如何编写继承
-->
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<script>
//封装继承
function inherit(Child,Parent){
//WsxString的原型指向=objectprototype 经过setprototypeof由指向的object原型指向到User，Vip原型上
Object.setPrototypeOf(Child.prototype,Parent.prototype)
}
function User(username,password){
this.name = username
this.password = password
}
function VipUser(username,password,member){
//username和password重复了，只保留一下
User.call(this,username,password)
this.member = member
}
User.prototype.wsxString = function(){
console.log('可看免费视频')
}
VipUser.prototype.wsxString = function(){
console.log('观看付费视频')
}
inherit(VipUser,User)
var user = new User('12','34')
console.log(user)
user.wsxString()
var VipUser = new VipUser('56','78','2024-02-13')
console.log(VipUser)
VipUser.wsxString();
</script>
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