How to check if a scope variable is undefined in AngularJS template?

Question

How to check if a scope variable is undefined?

This does not work:

<p ng-show="foo == undefined">Show this if $scope.foo == undefined</p>

Answer 1

Here is the cleanest way to do this:

<p ng-show="{{foo === undefined}}">Show this if $scope.foo === undefined</p>

No need to create a helper function in the controller!