JSFiddle - React, Tailwind, and code Playground

HTML

<html ng-app="demo">
<body ng-controller="ctrl">
  <h2>Just demo to check if foo is defined or not.</h2>
  <div ng-show="foo || undefined">
    Show this if foo is undefined and not shown!
  </div>
    <div ng-show="foo || !undefined">
    Show this if foo is undefined!
  </div>
</body>
</html>

JavaScript

angular.module("demo", [])
	.controller("ctrl", function ($scope) {
  	$scope.foo = undefined;
  });