title: What does (+var) means
body: <p>I'm new into the javascript world and I have not found any information about this notation.
  I found it in that topic (see the answer): <a href="https://stackoverflow.com/questions/9640266/convert-hhmmss-string-to-seconds-only-in-javascript">Convert HH:MM:SS string to seconds only in javascript</a>. </p>
  
  <pre><code>// minutes are worth 60 seconds. Hours are worth 60 minutes.
  var seconds = (+a[0]) * 60 * 60 + (+a[1]) * 60 + (+a[2]); 
  </code></pre>
  
  <p>Also I wanted to use that code to convert 'HH:MM:SS' string to seconds. But, it seems unsafe for me. If the user inserts 'XX:03:SS', the value will be NaN which is not correct (at least for me). So I decided to improved it with: </p>
  
  <pre><code>function convertHHMMSSToSeconds(time) {
  
  // initialize seconds
  var seconds = 0;
  
  //ensure time
  if (!time) {
      return seconds;
  }
  
  
  try {
      var hmsTab = time.split(':'); // split it at the colons
  
      // ensure that the hmsTab contains 3 values (hh,mm,ss)
      if (!hmsTab || hmsTab.length !== 3) {
          return seconds;
      }
  
      // initialize hh, mm and ss
      var hh = hmsTab[0] &gt; 0 &amp;&amp; hmsTab[0] &lt; 60? +hmsTab[0] : 0;
      var mm =  hmsTab[1] &gt; 0 &amp;&amp; hmsTab[1] &lt; 60 ? +hmsTab[1] : 0;
      var ss =  hmsTab[2] &gt; 0 &amp;&amp; hmsTab[2] &lt; 60 ? +hmsTab[2] : 0;
  
      // return 0 if one variable is not valid 
      if(+hmsTab[0] !== hh ||+hmsTab[1] !== mm || +hmsTab[2] !== ss) {
          return seconds;
      }
  
      // minutes are worth 60 seconds. Hours are worth 60 minutes.
      seconds = (hh * 60 * 60) + (mm * 60) + ss;
  }catch (error)
  {
      seconds = 0;
  }
  return seconds &amp;&amp; seconds&gt;0 ? seconds : 0;
  </code></pre>
  
  <p>}</p>
  
  <p>So my question still remains, what does (+var) mean.</p>
  
  <p>Regards,</p>