Javascript Parse Facebook Login Issue

After the new Developer portal updates, the OAuth redirect URIs can now be found under

Products > Facebook Login > Settings > Client OAuth Settings

or you can access via url: https://developers.facebook.com/apps/{appid}/fb-login/

I'm also faced this problem. On my situation site url writen with "www".If you site adress http://example.com then http://www.example.com is different website for facebook sdk. In facebook application console go

Settings > Advanced > Client OAuth Settings >Valid OAuth redirect URIs

Write here www version also. It must work

I also faced the error while trying to integrate Facebook login on my localhost in a Rails app and fixed it by removing the trailing slash from the URL specified in Valid OAuth redirect URIs

It was: http://localhost:3000/auth/facebook/callback/

It was supposed to be http://localhost:3000/auth/facebook/callback

Thanks to @CBroe comment to check the redirect_uri and found that in the URL in the browser's address bar it was

https://www.facebook.com/dialog/oauth?client_id=<my_app_client_id>&redirect_uri=http://localhost:3000/auth/facebook/callback&response_type=code&scope=email&state=afcbee26c2ce5077f844ce864780082991d36e6c3e10863a

and in my Valid OAuth redirect URIs it was mentioned http://localhost:3000/auth/facebook/callback/ (note the trailing slash at the end)

Hope this helps anyone facing this problem with the URL problem I had.