159453 Toggle Text Link When Clicked

Hello, I'm looking for a javascript effect where the user is able to toggle between "Expand" and "Collapse" when the link is clicked. For instance, the user will initially see "Expand". When the user clicks on that "Expand" link, the link changes to "Collapse". Clicking on that "Collapse" link again will revert back to "Expand" -- so it toggles.