异步组合使用
function sleep(duration){
return new Promise(function(resolve){
setTimeout(resolve, duration);
})
}
async function changeColor(duration,color){
document.getElementById("traffic-light").style.background = color;
await sleep(duration);
}
async function main(){
while(true){
await changeColor(3000,"green");
await changeColor(1000, "yellow");
await changeColor(2000, "red");
}
}
main()
