使用Promise过程中resolve或reject后，后面代码还会执行，默认加return较妥

    console.log(111)
    p()
      .then(result => {
        console.log(`p result:${result}`)
      })
      .catch(err => {
        console.log(`p err :${err}`)
      })
    p1()
      .then(result => {
        console.log(`p1 result:${result}`)
      })
      .catch(err => {
        console.log(`p1 err :${err}`)
      })
    p2()
      .then(result => {
        console.log(`p2 result:${result}`)
      })
      .catch(err => {
        console.log(`p2 err :${err.message}`)
      })
    function p() {
      return new Promise((resolve, reject) => {
        console.log(222)
        setTimeout(() => {
          console.log('async in p')
          reject('err in p')
          console.log('content after p reject')
        }, 200)
      })
    }
    function p1() {
      return new Promise((resolve, reject) => {
        console.log(333)
        setTimeout(() => {
          console.log('async in p1')
          resolve('resolev in p1')
          console.log('content after p1 resolve')
        }, 250)
      })
    }
    function p2() {
      return new Promise((resoleve, reject) => {
        console.log(444)
        setTimeout(() => {
          console.log('async in p2')
          return reject(new Error('p2error'))
          console.log('content after p2 return')
        }, 300)
      })
    }