title: How to return a result of async function (async module) in nodeJs
body: <p>I used async module for my project. This is my code in file 1</p>
  
  <pre><code>exports.check = function(option){
      var object = {};
      async.parallel([
          function(callback){
              if(!option.one){callback(null, true);}else{ callback(null, false);}
          },
          function(callback){
              if(!option.two){callback(null, true);}else{ callback(null, false);}
          },
          function(callback){
              if(!option.three){callback(null, true);}else{ callback(null, false);}
          }
      ],
      function(err, results){
          if(results[0] &amp;&amp; results[1] &amp;&amp; results[2] ){
              object.one = results[0];
              object.two = results[1];
              object.three = results[2];
              object.total = true;
  
          }else{
              object.one = results[0];
              object.two = results[1];
              object.three = results[2];
              object.total = false;
  
          }
      })
      return object;
  }
  </code></pre>
  
  <p>And This is code in file 2. I use function in file 1:</p>
  
  <pre><code>var isexit = db.check(option);
      console.log(isexit);
  </code></pre>
  
  <p>A problem is console is <strong>'undefined'</strong>. 
  If I change code in file 1 to be the line (<strong>return object</strong>):</p>
  
  <pre><code>exports.check = function(option){
      var object = {};
      async.parallel([
          function(callback){
              if(!option.one){callback(null, true);}else{ callback(null, false);}
          },
          function(callback){
              if(!option.two){callback(null, true);}else{ callback(null, false);}
          },
          function(callback){
              if(!option.three){callback(null, true);}else{ callback(null, false);}
          }
      ],
      function(err, results){
          if(results[0] &amp;&amp; results[1] &amp;&amp; results[2] ){
              object.one = results[0];
              object.two = results[1];
              object.three = results[2];
              object.total = true;
  
          }else{
              object.one = results[0];
              object.two = results[1];
              object.three = results[2];
              object.total = false;
  
          }
         return object;
      })
  
  }
  </code></pre>
  
  <p>It will error. So How to return a funciton result in file 1. Pls help. Thanks so much!</p>