Immediately check if field content already exists in a node form I am struggling with a problem which I thought might be answered simply... Any help would be appreciated!

I have a content type called 'review'. Each review has a field called 'location'. As a user creates a new review, once they have filled in the location field, I would like a small message to appear in case that same user has already created a review for the same location.

Doing it when the user is about to save the node is not too complicated. But I actually want it to happen as soon as the relevant field is not empty.

Thanks
You can write little custom jQuery snippet using 'blur' event in order to do this. More information you may find on this page http://www.w3schools.com/jquery/event_blur.asp