Promise async await tutorial

paat.js

// Promise, async, await 快速教程
// 包含异步执行顺序控制、异常控制、多异步排序控制

// t1 多异步串行、异常处理
function t1(){
  function stepA(){ 
    return new Promise((resolve, reject) => {
      setTimeout(()=>{
        Math.random() > 0.5 ? resolve('A') : reject('~A~')
      }, 300)
    })
  }
  function stepB(pre){
    return new Promise((resolve, reject) => {
      setTimeout(()=>{
        resolve(pre + 'B')
      }, 100)
    })
  }

  async function runAB(){
      let A
      try{
        A = await stepA()
      } catch (e) {
        A = e
      }
      const B = await stepB(A)
      console.log(B)
  }

  function stepC(){
    return new Promise((resolve, reject) => {
      runAB().then(()=>{resolve('done C')})
    })
  }

  async function runC(){
    let c = await stepC()
    console.log(c);
  }

  runC()
}
// t1()

// 多异步并行、异常
function t2(){
  function s1(){
    return new Promise((r, rj)=>{
      setTimeout(()=>{
        Math.random() > 0.5 ? r('s1') : rj('s1')
        console.log('s1')
      }, 50)
    })
  }
  function s2(){
    return new Promise((r, rj)=>{
      setTimeout(()=>{
        r('s2')
        console.log('s2')
      }, 100)
    })
  }
  function run(){
    Promise.all([s1(), s2()]).then(()=>{
      console.log('done')
    }).catch(err=>{
      console.error(err.toString())
    })
  }
  run()
}
t2()