Function getParentNodeAriaLevel

src/cdk/tree/tree.ts:1493–1510

(nodeElement: HTMLElement)

}

function getParentNodeAriaLevel(nodeElement: HTMLElement): number {
  let parent = nodeElement.parentElement;
  while (parent && !isNodeElement(parent)) {
    parent = parent.parentElement;
  }
  if (!parent) {
    if (typeof ngDevMode === 'undefined' || ngDevMode) {
      throw Error('Incorrect tree structure containing detached node.');
    } else {
      return -1;
    }
  } else if (parent.classList.contains('cdk-nested-tree-node')) {
    return numberAttribute(parent.getAttribute('aria-level')!);
  } else {
    // The ancestor element is the cdk-tree itself
    return 0;
  }
}

function isNodeElement(element: HTMLElement) {
  const classList = element.classList;