createNodeIterator.js

/**
 * Node を順に列挙する
 *
 * @param {Node} root
 * @param {?{ whatToShow?: number, filter?: NodeFilter, direction?: "capture" | "bubbling" }} options
 * @param {"capture" | "bubbling"} options.direction - "capture" では現れる順に列挙し、 "bubbling" では子を持つ Node は子から列挙する
 * @return {Generator<Node>}
 */
function* createNodeIterator(root, options = {}) {
  const { whatToShow, filter } = options;
  const direction = options.direction === "bubbling" ? "bubbling" : "capture";

  if (direction === "capture") {
    const iterator = document.createNodeIterator(root, whatToShow, filter);
    for (;;) {
      const current = iterator.nextNode();
      if (current !== null) {
        yield current;
      } else {
        return;
      }
    }
  } else {
    const walker = document.createTreeWalker(root, whatToShow, filter);
    for (;;) {
      while (walker.firstChild() !== null) {}
      yield walker.currentNode;
      while (walker.nextSibling() === null) {
        const current = walker.parentNode();
        if (current !== null) {
          yield current;
        } else {
          return;
        }
      }
    }
  }
}