JavaScript:

以下测不出效果, 因为程序逻辑是在function two中执行

<script>
    function one () {
      console.info('one')
    }
    function two () {
      setTimeout(() => {
        console.info('two')
      }, 1)
    }
    function three () {
      console.info('three')
    }
    function run () {
      one()
      two()
      three()
    }
    run()
  </script>

 

假设run需要拿到two的执行结果, 进行操作

<script>
    function one () {
      return 'one'
    }
    function two () {
      setTimeout(() => {
        return 'two'
      }, 1)
    }
    function three () {
      return 'three'
    }
    function run () {
      console.log(one())
      console.log(two())
      console.log(three())
    }
    run()
  </script>

 

 

利用async await Promise将程序改造成同步

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    function one () {
      return 'one'
    }
    function two () {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          resolve('resolve two')
          // return 'two'
        }, 2000)
      })
    }
    function three () {
      return 'three'
    }
    async function run () {
      console.log(one())
      console.log(await two())
      console.log(three())
    }
    run()
  </script>
</body>

</html>

 

posted @ 2022-03-19 08:44  ascertain  阅读(24)  评论(0)  编辑  收藏  举报