lovecoding
/
VIP30


			
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							<!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>
    // console.log(4)
    // setTimeout(()=>{
    //   console.log(1)
    //   setTimeout(()=>{
    //     console.log(2)
    //   },100)
    //   setTimeout(()=>{
    //     console.log(3)
    //   },10)
    // },0)
    // console.log(5)

    // let p1 = new Promise ((resolve,reject)=>{
    //   reject()
    //   resolve()
    // }).then(()=>{
    //   console.log('我成功了')
    // }).catch(()=>{
    //   console.log('我失败了')
    // })
    /* 
      promise 有三种状态
        pending 进行中
        fullfiled 已经成功
        rejected  已经失败
      pending ->  fullfiled  or  pending -> rejected 
      不可逆的  
      1.当一个promise 被创建的时，初始状态为pending
      2.当异步操作执行成功的时候，promise状态变为fullfiled 并且执行
      then方法中回调函数
      3.当异步操作执行失败的时候，promise状态变为rejected 并且执行
      catch方法中的回调函数
    */
    let p1 = new Promise((resolve, reject) => {
      setTimeout(()=>{
        console.log(1)
        reject()
      },1000)
      console.log(2)
      resolve()

    })
    let p2 = new Promise ((resolve,reject)=>{
      setTimeout(()=>{
        console.log(3)
        reject()
      },800)
      reject()
    })
    let p3 = new Promise ((resolve,reject)=>{
      setTimeout(()=>{
        console.log(4)
        resolve()
      },2000)
      console.log(5)
      reject()
    })
  
    /* promise.all()将多个promise实例封装成一个promise实例 */
    Promise.all([p1,p2,p3]).then(()=>{
      console.log('ok')
    }).catch(()=>{
      console.log('error')
    })
/* 
    Promise.race([p1,p2,p3]).then(()=>{
      console.log('ok')
    }).catch(()=>{
      console.log('error')
    }) */


    // new Promise((resolve,reject)=>{
    //   setTimeout(()=>{
    //     console.log(1)
    //     resolve()
    //   },10)
    // }).then(()=>{
    //   console.log('ok')
    // }).catch(()=>{
    //   console.log('error')
    // })
  </script>
</body>

</html>