Angular: Empty Fiddle

http://angularjs.org/

HTML

<script src="http://code.angularjs.org/angular-1.0.1.js"></script>
<div ng-controller="MyCtrl">
  
  <button class="btn btn-default" type="button" name="Test" value="Test" ng-click="isTimeValid('00:40')"></button>
	 
		{{validState}}
  
</div>

JavaScript

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

//myApp.directive('myDirective', function() {});
//myApp.factory('myService', function() {});

function MyCtrl($scope) {
    $scope.name = 'Superhero';
    
    $scope.validState = false;
		  
		  $scope.isTimeValid = function (timeString) {
		  
			var regex_time =/^([0-9]{2})\:([0-9]{2})$/;
			if(regex_time.test(timeString) == false) {
				$scope.validState = false;
				return false;
			}
			var parts = timeString.split(":");
			var hours = parseInt(parts[0], 10);
			var minutes = parseInt(parts[1], 10);
			if(hours > 0 && hours < 24 && minutes >= 0 && minutes < 60) {
				$scope.validState = true;
				return true;
			}
			$scope.validState = false;
			return false;
		} 
    
}