Execute an expression at every keystroke:
Definition and Usage
ng-keydown directive tells AngularJS what to do when the
keyboard is used on the specific HTML element.
ng-keydown directive from AngularJS will not override the element's original onkeydown event, both will be executed.
The order of a key stroke is:
Supported by <input>, <select>, <textarea>, and other editable elements.
|expression||An expression to execute when a key is pressed.|