How does GWT "know" which DOM element you've just selected?

Question

It has been a while since I've touched GWT, but I was recently looking at GWT applications to see how they accomplished certain tasks. I noticed that if you go into AdWords (a GWT application), you can manipulate table information in-line. For example, if I go into my campaign and click the pencil icon next to the ad group, a little popup will appear allowing me to change the ad group's name ... except there's no identifying information anywhere in the DOM structure. No hidden fields, no id's snuck into the div elements.

What's going on here? I've been working with interactive tables, but I've always established a click handler on a class and stuck an ID in there so I can tell what I'm editing. I've always found this as unsatisfactory. Any ideas?

Answer 1

It uses a JavaScript variable to get a hold on the element directly when it's created. That variable can then be stored somewhere - as long as it's accessible directly or indirectly from the the global object (document), it can be retrieved later from there.

A simple pure JavaScript example would be:

document.myParagraph = document.createElement('p');
document.body.appendChild(myParagraph);

document.mySpan = document.createElement('span');
document.myParagraph.appendChild(mySpan);

...

document.mySpan.onclick = ...