Angular: Empty Fiddle

http://angularjs.org/

HTML

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.3/angular.min.js"></script>
<input ng-init="customTag='u'" type="text" ng-model="customTag" placeholder="Enter a name here" ng-change="update()"/>
<span render="{{customTag}}">77</span>

JavaScript

var myApp = angular.module('myApp',[]);

myApp.directive('render', function() {
    return {
        restrict: 'A',
        link: function(scope, element, attrs) {
            attrs.$observe('render', function(value) {
                if (value) {
                    element.html('<' + value + '>77</' + value + '>');      
                } else {
                    element.html(77);      
                }              
            });
        }
    };
});