延迟函数 等待多久后执行XXX

    1. const delay = function delay(interval = 1000) {
    2.   return new Promise((resolve) => {
    3.     setTimeout(() => {
    4.       resolve()
    5.     }, interval)
    6.   })
    7. }
    11. //用法举例
    12. delay(3000).then(()=>{
    13.   console.log(1)
    14. })
    16. const fn = async () => {
    17.   let res = await delay(2000)
    18.   console.log(2)
    19. }
    20. fn()