title: how to find a single field in mongoDB instead of entire document
body: <p>I want to achieve the result as obtained by</p>
  
  <pre><code>SELECT AGE FROM COLL WHERE NAME="AYUSH";
  </code></pre>
  
  <p>I took the following approach</p>
  
  <pre><code>var MongoClient = require('mongodb').MongoClient;
  var url = "mongodb://localhost:27017/";
  
  MongoClient.connect(url, function(err, db) {
    if (err) throw err;
    var dbo = db.db("new");
    //var query = { name:'ayush' };
    //var age = {age : 1, _id:0};
    dbo.collection("coll").find( 
         { name:'ayush' },
         { age : 1, _id:0}).toArray(function(err, result) {
      if (err) throw err;
      console.log(result);
      db.close();
    });
  });
  </code></pre>
  
  <p>the result that i am getting is</p>
  
  <pre><code>[ { _id: 5a818b71d2029813505d736a,
  name: 'ayush',
  age: '22',
  sex: 'm' } ]
  </code></pre>