Angular directive for min digits validation in input type number

minDigitsDirective.js

/*
<input type='number' min-digits='4' />
*/
.directive("minDigits", function () {
	return {
		require: "ngModel",
		link: function (scope, element, attrs, ctrl) {
			var min = attrs.minDigits;

			element.bind("keyup", function () {
				var currentValue = element.val();
				var v = currentValue.length >= min;

				scope.$apply(function () {
					ctrl.$setValidity("mindigits", v);
				});
			});
		}
	}
})