title: How to lower case a string in Typescript?
body: <p>I am comparing two strings and I want to lower case a string before comparing. How can I do this? 
  This is my code:</p>
  
  <pre><code> this.products = response.responseData.sort(function(a,b){
  
                       if(a.product.productName &lt; b.product.productName){
                           return -1;
                       }
                       if(a.product.productName &gt; b.product.productName){
                           return 1;
                       }
                       return 0;
                   });
  </code></pre>