1. const Gen = time => {
    2.   return new Promise((resolve, reject) => {
    3.     setTimeout(function() {
    4.       if (time < 500) {
    5.         reject(time);
    6.       } else {
    7.         resolve(time);
    8.       }
    9.     }, time);
    10.   });
    11. };
    13. Gen(Math.random() * 1000)
    14.   .then(val => console.log("resolve", val))
    15.   .catch(err => console.log("reject", err))
    16.   .finally(() => {
    17.     console.log("finish");
    18.   });