使用定時函式模擬非同步請求

• 回撥函式

  function doSomething(callback){
      setTimeout(function(){
          console.log('執行結束');
          let result = 4;
          callback(result);
      },100);
  }
  
  function callback(result){
      console.log('接收到結果為：'+result);
  }
  
  doSomething(callback);
  
  //doSomething((result)=>{console.log('接收到結果為：'+result)});
   
  

• 使用es6提供的Promise函式

  function doSomething(){
  
      return new Promise(function(resolve){
          setTimeout(function(){
              console.log('執行結束');
              let result = 6;
              resolve(result);
          },100);
      });
  
  }
  
  doSomething().then(result=>{
      console.log('接收到結果為：'+result);
  });
   
  

• Generator函式

  function doSomething(){
      setTimeout(function(){
          let result = 6;
          it.next(result);
      },100);
  }
  
  function *gener(){
      var result = yield doSomething();
      console.log(result);
  }
  
  let it = gener();
  it.next();
  

• 使用es7新特性async

  function doSomething(){
      return new Promise(resolve=>{
          setTimeout(function(){
              let result = 6;
              resolve(result);
          },100);             
      });
  
  }
  
  async function action(){
      let result = await doSomething();
      console.log(result);
  }
  action();