<!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>练习</title> </head>
<style>
.light{
width:200px;
height: 200px;
border-radius:50%;
background:red;
}
.light2{
width:200px;
height: 200px;
border-radius:50%;
background:red;
}
</style>
<body>
<div class="light"></div>
<div class="light2"></div>
<script>
//promise实现 红绿灯
var light=document.getElementsByClassName("light")[0];
var r=function(){
return new Promise(function(resolve,reject){
light.style.background="red";
setTimeout(resolve,3000);
})
};
var y=function(){
return new Promise(function(resolve,reject){
light.style.background="yellow";
setTimeout(resolve,2000);
})
}
var g=function(){
return new Promise(function(resolve,reject){
light.style.background="green";
setTimeout(resolve,4000);
})
}
var xun=function(){
r().then(function(){
return y();
}).then(function(){
return g();
}).then(function(){
return xun();
});
}
xun(); //async/await实现红绿灯
const lignt2=document.getElementsByClassName("light2")[0];
function changeLightColor(color,duration){
return new Promise(function(resolve,reject){
lignt2.style.background=color;
setTimeout(resolve,duration);
})
} async function xun2 (){
await changeLightColor("red",3000);
await changeLightColor("yellow",2000);
await changeLightColor("green",4000);
xun2();
}
xun2();//执行
</script>
</body>
</html>