Get User Email id on clicking FaceBook 'Like' button?

I want the email address of the user when he/she clicks on the facebook Like button.

Here is the code I'm 开发者_开发问答using:

FB.Event.subscribe('edge.create', function(response) {
  // like clicked
});

But the response only has the HREF.

How do I do this?

Simply you can't!

Even if the user is going to allow/authorize your application and you were asking for their emails (email permission), users may choose not to share it with you and provide you a proxied Facebook email address instead!