With AngularJS's two-way data binding, it's very easy to count the characters while user is typing. Usually this will need to use JavaScript to watch keyup event on input or textarea elements. But with AngularJS, it's very simple. No JavaScript is required.

As code shown below, use ng-model to bind textarea to model message. Once message is changed by user input, {% raw %}{{ message.length }}{% endraw %} will display characters count.

<div>{% raw %}{{ message.length }}{% endraw %} of 120</div>  
<textarea ng-model="message" cols="30" rows="10"></textarea>  

See this JSFiddle for the code.