web-vitals/src/lib/getSelector.ts

/*
 * Copyright 2022 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const getName = (node: Node) => {
  const name = node.nodeName;
  return node.nodeType === 1
    ? name.toLowerCase()
    : name.toUpperCase().replace(/^#/, '');
};

export const getSelector = (node: Node | null | undefined, maxLen?: number) => {
  let sel = '';

  try {
    while (node && node.nodeType !== 9) {
      const el: Element = node as Element;
      const part = el.id
        ? '#' + el.id
        : getName(el) +
          (el.className && el.className.length
            ? '.' + el.className.replace(/\s+/g, '.')
            : '');
      if (sel.length + part.length > (maxLen || 100) - 1) return sel || part;
      sel = sel ? part + '>' + sel : part;
      if (el.id) break;
      node = el.parentNode;
    }
  } catch (err) {
    // Do nothing...
  }
  return sel;
};