title: Ext.String.format enhancement in EXTJS
body: <p>I am new to ExtJS. I came across following piece of code:</p>
  
  <pre><code>Ext.String.format('&lt;a href="mailto:{0}"&gt;{1}&lt;/a&gt;',value+"@abc.com",value);
  </code></pre>
  
  <p>Now this will create a mailto link. But my query is that how Ext.String.format works and what else can I use it for?</p>