(keydown) = "onKeydown($event)" meaning angular code example
Example 1: javascript onkeydown
<input type="text" onkeydown="myFunction()">
Example 2: onkeydown angularjs
<ANY
ng-keydown="expression">
...
</ANY>
<input type="text" onkeydown="myFunction()">
<ANY
ng-keydown="expression">
...
</ANY>