javascript 函数生命周期（JavaScript sleep睡眠函数的使用）

// setTimeout
let fun = () => console.log('time out');
let sleep = function(fun,time){
  setTimeout(()=>{
    fun();
  },time);
}

sleep(fun,2000);

setTimeout
setTimeout是最基本的实现方式，代码如下，使用递归来实现循环改变颜色：
function changeColor(color) {
 console.log('traffic-light ', color);
}
function main() {
 changeColor('red');
 setTimeout(()=>{
  changeColor('yellow');
  setTimeout(() => {
   changeColor('green');
   setTimeout(main, 2000);
  }, 1000);
 }, 2000);
}
main();

// promise
let fun = () => console.log('time out');
let sleep2= (time)=> new Promise((resolve)=>{
  setTimeout(resolve,time)
})
sleep2(2000).then(fun);

const traffic_light=(color,duration)=>{
  return new Promise((resolve,reject)=>{
    console.log('traffic-light ', color);
    setTimeout(()=>{
        resolve()
    },duration)
  })
}
const main=()=>{
    Promise.resolve()
    .then(()=>{
        return traffic_light('red',3000)
    })
    .then(()=>{
        return traffic_light('yellow',1000)
    })
    .then(()=>{
        return traffic_light('green',2000)
    })
    .then(()=>{
        main();
    })
}
main()

// async await
async function wait(time){
  await sleep2(time);
  fun();
}

wait(3000);

function sleep(duration) {
  return new Promise(resolve => {
      setTimeout(resolve, duration);
  })
}
async function changeColor(color, duration) {
 console.log('traffic-light ', color);
 await sleep(duration);
}
async function main() {
 while (true) {
  await changeColor('red', 2000);
  await changeColor('yellow', 1000);
  await changeColor('green', 3000);
 }
}
main();

const log = console.log;
const sleep = (timeout) => {
  return new Promise((resolve)=>{
    setTimeout(()=>{
      resolve();
    }, timeout)
  })
}

const main = async()=>{
  await sleep(1000);
  log(1);
  await sleep(2000);
  log(2);
  await sleep(3000);
  log(3);
}