Promise实现队列

 var promise=doSomething();
  promise=promise.then(doSomethingElse);
  promise=promise.then(doSomethingElse2);
  promise=promise.then(doSomethingElse2);

 function queue(things){
   let promise=Promise.resolve();
   things.forEach(element => {
    promise=promise.then(()=>{
      return new Promise(resolve=>{
        setTimeout(() => {
          console.log(element)
          resolve(‘ok‘);
        }, 1000);
      });
    })
   });
 }
  queue([‘h1‘,‘h2‘,‘h3‘]);