Function isRelevantSelectMutation

packages/forms/signals/src/directive/select.ts:53–80

* Checks if a given mutation record is relevant for resyncing a . * In general its relevant if: * - Non comment content of the select changed * - The value attribute of an option changed.

(mutation: MutationRecord)

 * - The value attribute of an option changed.
 */
function isRelevantSelectMutation(mutation: MutationRecord) {
  // Consider changes that may add / remove options, or change their text content.
  if (mutation.type === 'childList' || mutation.type === 'characterData') {
    // If the target element is a comment it's not relevant.
    if (mutation.target instanceof Comment) {
      return false;
    }
    // Otherwise if any non-comment nodes were added / removed it is relevant.
    for (const node of mutation.addedNodes) {
      if (!(node instanceof Comment)) {
        return true;
      }
    }
    for (const node of mutation.removedNodes) {
      if (!(node instanceof Comment)) {
        return true;
      }
    }
    // Otherwise it's not relevant.
    return false;
  }
  // If the value attribute of an option changed, it's relevant.
  if (mutation.type === 'attributes' && mutation.target instanceof HTMLOptionElement) {
    return true;
  }
  // Everything else is not relevant.
  return false;
}