一个简单的例子来使用ES6的Promise object.

var p = new Promise(function(resolved,rejected){
  
  var random = Math.floor(Math.random() * Math.floor(2));
  
  console.log(random);
  
  setTimeout(function(){
    if(random === 1) resolved('resolved');
    if(random === 0) rejected('rejected');
  },2000);
  
})

p.then(
  function(data){
    console.log(data);
  },
  function(error){
    console.log(error);
  }
);