Handling Exceptions

Handling Exceptions

DOM methods report failures by throwing a DOMException, identified by its name. Each trigger below was tested in Chrome 1 .

Common DOMException names
name	code	Example trigger
IndexSizeError	1	buffered.end(0) with no data
HierarchyRequestError	3	Appending <html> to <body>
InvalidCharacterError	5	createElement('1st')
SyntaxError	12	querySelector('##')
AbortError	20	signal.throwIfAborted()
DataCloneError	25	structuredClone(() => {})

The numeric code is legacy (newer names such as NotAllowedError have 0), so branch on name. You can create your own, for example as an abort reason:

Creating and catching a DOMExceptionJavaScript

const controller = new AbortController();
controller.abort(new DOMException('Upload cancelled by user', 'AbortError'));
try {
  controller.signal.throwIfAborted();
} catch (err) {
  if (!(err instanceof DOMException)) throw err;     // rethrow non-DOM errors
  console.log(err.name, err.code, err.message);
}

Output

AbortError 20 Upload cancelled by user

Chrome now throws storage quota failures as a QuotaExceededError subclass (code 22) with quota and requested properties.

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