Note: This release is in preview. Features described here don’t become generally available until the latest general availability date that Salesforce announces for this release. Before then, and where features are noted as beta, pilot, or developer preview, we can’t guarantee general availability within any particular time frame or at all. Make your purchase decisions only on the basis of generally available products and features.

source Context Variable

Pass in any context and get it back in the callback method by using the source context variable.

For an example of how to use source in an error handling context, see Error Handling with the AJAX Toolkit.