js实现sleep功能

    class Test{
        constructor(){
            this.promise=Promise.resolve();
        }
        showSomething(something){
            this.promise=this.promise.then(()=>console.log(something));
            return this;
        }
        sleep(time){
            let p=new Promise((resolve,reject)=>window.setTimeout(()=>{console.log(`sleep ${time}`);resolve()},time*1000));
            this.promise=this.promise.then(()=>p);
            return this;
        }
    }
    const t=new Test();
    t.showSomething('aaa').sleep(3).showSomething('bbb').sleep(15).showSomething('xxxx');