SOURCE

var textFun = function(){
   let self = this;
   return new Promise((succ,erro)=>{
    setTimeout(()=>{
     document.write(self);
     succ.call(self,'this is result')
    },2000)
   })
  };
  textFun().then((request)=>{
   document.write(request);//this is result
  })
  class Cat{
    this.name = 'Tom';
  }
const cat = new Cate();
document.write(cate.name)