红绿灯任务控制

  1. function red(){
  2.     console.log('red')
  3. }
  4. function yellow(){
  5.     console.log('yellow')
  6. }
  7. function green(){
  8.     console.log('green')
  9. }
  11. const task = (timer, light) => {
  12.     return new Promise((resolve, reject) => {
  13.       setTimeout(() => {
  14.         if(light === 'red'){
  15.           red()
  16.       }else if (light === 'yellow'){
  17.           yellow()
  18.       }else if (light === 'green'){
  19.         green()       
  20.       }
  21.       resolve()
  22.     }, timer)
  23.   })
  24. }
  26. // promise
  27. const step = () => {
  28.     task(3000, 'red').then(() => {
  29.       task(1000, 'yellow')
  30.   }).then(() => {
  31.       task(2000, 'green')
  32.   }).then(step)
  33. }
  34. step()
  36. // async、await
  38. const step = async () => {
  39.     await task(3000, 'red')
  40.   await task(1000, 'yellow')
  41.   await task(2000, 'green')
  42.   step()
  43. }
  45. step()