<!DOCTYPE html>
<html>
<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>
<body ng-app="">
<form name="myForm">
Click here to make the input field required:
<input type="checkbox" ng-model="myVar"><br><br>
<input name="myInput" ng-model="myInput" ng-required="myVar">
<h1 ng-if="!myForm.myInput.$valid">The input field cannot be empty</h1>
</form>
<p>In this example, we will display an error if the field is empty AND the checkbox is checked for "required".</p>
</body>
</html>