 <p>Just a note, when using .mask() function, you have to call it to a DOM element, which means you should use it either with</p> <pre><code>Ext.get('yourDomElementId').mask(); </code></pre> <p>or</p> <pre><code>Ext.getCmp('yourExtComponentId').el.mask(); //this gets the dom //element attached to the component </code></pre> <p>I've never used it with .body</p>