title: Convert numeric string to number in angular 2
body: <p>I want to compare angular 2 expressions. I got array of data in numeric string from my database i need to convert this to number before give a condition with ngClass for styling. how can i convert this type. any idea?</p>
  
  <pre><code>  &lt;td [ngClass]= "{'positive': gbh.Last &gt; 0, 'negative': gbh.Last &lt; 0}"&gt; {{gbh.Last}} &lt;/td&gt;
  </code></pre>