类的继承

//class类的使用
class ai{
	constructor(hp,speed) {
	    this.hp = hp;
	    this.speed = speed;
	}
	
	move(){  //:function可以省略
		console.log(`速度是${this.speed}`)
		
	}
}			

class addai extends ai{   //继承父类ai
	constructor(hp,speed,attacs) {
	    super(hp,speed)   //通过super初始化父类
		this.attacs = attacs
	}
	attac(){
		console.log(`攻击力是${this.attacs}`)
	}
}

a1 = new ai(100,20)
a1.move()

a2 = new addai(200,30,10)
a2.move()
a2.attac()

promise承诺(异步请求)
例1：

//构造承诺
let p1 = new Promise( (resolve,reject)=>{
	setTimeout( ()=>{
		let i = Math.random();  //返回一个0~1的随机数
		if(i>0.5){
			resolve();
		}else{
			reject();
		}
	},2000 )
	
})
//取得承诺结果
p1.then( ()=>{console.log("成功")},()=>{console.log("失败")} )

例2：

//构造承诺
let p1 = new Promise( (resolve,reject)=>{
	//第一次第二次同时为好成功,有一次坏就失败
	let r1 = Math.random()
	if(r1>0.5){
		console.log("第一次好")
		let r2 = Math.random()
		if(r2>0.5){
			console.log("第二次好")
			resolve();
		}else{
		console.log("第二次坏")
		reject();
	}
	}else{
		console.log("第一次坏")
		reject();
	}
	
})
//取得承诺结果
p1.then( ()=>{console.log("成功")},()=>{console.log("失败")} )