title: query values in leveldb database in nodejs
body: <p>How could I query a levelDB database by values in nodejs? 
  I have key: value pairs in my leveldb database and I want to search some values in it and find that key-value pair from that result. I am a beginner in leveldb. </p>
  
  <pre><code>{
      "key1" : {
                   "data1": "value1",
                   "data2": "value2",
                   "data3": "value3"
               }
  }
  </code></pre>
  
  <p>So, I want to query value where data3 == value3 and get that key-value pair.</p>
  
  <p>In levelDB, we can only get data on the basis of key.
  Is there any other alternative?</p>