搜索await page.waitForSelector(allResultsSelector);

/**
 * Copyright 2017 Google Inc. All rights reserved.
 *
 * 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
 *
 *     http://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.
 */

/**
 * @fileoverview Search developers.google.com/web for articles tagged
 * "Headless Chrome" and scrape results from the results page.
 */

'use strict';

const puppeteer = require('puppeteer');

(async() => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  await page.goto('https://developers.google.com/web/');

  // Type into search box.---输入文字 还有提换方法
  //await page.focus('#kw');
  //await page.keyboard.sendCharacter('狗');
  await page.type('#searchbox input', 'Headless Chrome');

  // Wait for suggest overlay to appear and click "show all results".
  const allResultsSelector = '.devsite-suggest-all-results';
//等待元素加载
  await page.waitForSelector(allResultsSelector);
  await page.click(allResultsSelector);

  // Wait for the results page to load and display the results.
  const resultsSelector = '.gsc-results .gsc-thumbnail-inside a.gs-title';
  await page.waitForSelector(resultsSelector);

  // Extract the results from the page.
  const links = await page.evaluate(resultsSelector => {
    const anchors = Array.from(document.querySelectorAll(resultsSelector));
    return anchors.map(anchor => {
      const title = anchor.textContent.split('|')[0].trim();
      return `${title} - ${anchor.href}`;
    });
  }, resultsSelector);
  console.log(links.join('\n'));

  await browser.close();
})();