Promise

原文链接: MDN

Promise
状态	pending, fulfilled, rejected
作用	代理对象（值），解决异步回调
特点	链式调用，成功(onfulfilled)和失败(onrejected)绑定相应处理方法

方法	优、缺点
Promise.all(iterable)	处理异步队列成功会返回一个promise对象（值为数组，顺序与队列一致）。队列中任一task出错将触发promise失败，仅返回出错task的错误信息
Promise.race(iterable)	返回最早返回值的task信息(不论成功失败)
Promise.reject(reason)

    let successQuery = () => {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          resolve('successQuery')
        }, 1000)
      })
    }
    let errorQuery = () => {
      return new Promise((resolve, reject) => {
          reject('errorQuery')
      })
    }
    Promise.all([successQuery(), errorQuery()]).then(data => {
      console.log('success: ', data)
    }).catch(error => {
      console.log('error: ', error)
    })
    //error:  errorQuery

    //Promise.race(iterable)
    //@(1)
     let successQuery = () => {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          resolve('successQuery')
        }, 3000)
      })
    }
    let errorQuery = () => {
      return new Promise((resolve, reject) => {
          setTimeout(() => {
          reject('errorQuery')
        }, 2000)
      })
    }
    Promise.race([successQuery(), errorQuery()]).then(data => {
      console.log('success: ', data)
    }).catch(error => {
      console.log('error: ', error)
    })
    // error:  errorQuery

    //@(2)
    let successQuery = () => {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          resolve('successQuery')
        }, 1000)
      })
    }
    let errorQuery = () => {
      return new Promise((resolve, reject) => {
          setTimeout(() => {
          reject('errorQuery')
        }, 2000)
      })
    }
    Promise.race([successQuery(), errorQuery()]).then(data => {
      console.log('success: ', data)
    }).catch(error => {
      console.log('error: ', error)
    })
    // success:  successQuery