How to disable an input box using angular.js

Use ng-disabled or a special CSS class with ng-class

<input data-ng-model="userInf.username"  
       class="span12 editEmail" 
       type="text"  
       placeholder="me@example.com"  
       pattern="[^@]+@[^@]+\.[a-zA-Z]{2,6}" 
       required 
       ng-disabled="{expression or condition}"
/>