They get added as attributes to "document", they're not truly global: https://stackoverflow.com/questions/3434278/do-dom-tree-elements-with-ids-become-global-pr

They get added as attributes to "document", they're not truly global: https://stackoverflow.com/questions/3434278/do-dom-tree-elements-with-ids-become-global-properties https://stackoverflow.com/questions/3434278/do-dom-tree-elem... Part of why IDs are supposed to be unique on a page.