What are DOM levels?

Question

I\'ve heard DOM level 2 and DOM level 3 mentioned in previous posts. Are these abstract constructs like the ISO OSI model which has layers 1-7 but are only loosely followed?

Answer 1

DOM Levels are essentially versions.

DOM Level 1 defines the core elements of the Document Object Model. DOM Level 2 extends those elements and adds events. DOM Level 3 extends DOM lvl 2 and adds more elements and events.

Each new level of the DOM adds or changes specific sets of features. When browsers are said to be DOM Level X compliant developers can (hopefully) assume that the browser correctly handles the specified DOM api calls.