JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app="testApp" ng-controller="testCtrl">
    <test-dir identity="one" optional="myFlag"></test-dir>
    <test-dir identity="two"></test-dir>
</div>

JavaScript

angular.module("testApp", [])
.controller("testCtrl", ["$scope", function testCtrl($scope) {
    $scope.myFlag = false;
}])
.directive("testDir", function testDir() {
    return {
        restrict: "EA",
        scope: {
            identity: "@",
            optional: "=?"
        },
        link: function testDirLink($scope, $element, $attrs) {
            if (typeof $scope.optional == "undefined") {
                $scope.description = "optional was undefined";
            }
            else {
                $scope.description = "optional = '" + $scope.optional + "'";
            }
        },
        template: "<div>{{identity}} - {{description}}</div>"
    };
});