ng-empty | ng-filled

angular-is-input-filled.js

app.config(function($provide) {
	$provide.decorator('ngModelDirective', function($delegate) {
		var last = $delegate[0].controller.length - 1,
			controller = $delegate[0].controller[last],
			EMPTY_CLASS = 'ng-empty',
			NON_EMPTY_CLASS = 'ng-filled';

		$delegate[0].controller[last] = function($scope, $exceptionHandler, $attrs, $element, $parse, $animate) {
			controller.apply(this, arguments);
			var context = this,
				toggle = function (value) {
					if (context.$isEmpty(value)) {
						$animate.removeClass($element, NON_EMPTY_CLASS);
						$animate.addClass($element, EMPTY_CLASS);
					} else {
						$animate.removeClass($element, EMPTY_CLASS);
						$animate.addClass($element, NON_EMPTY_CLASS);
					}
					return value;
				};

			this.$formatters.push(toggle);
			this.$parsers.push(toggle);
		};

		return $delegate;
	});
});