puppeteer/examples/unrandomize.js

/**
 * Copyright 2017 Google Inc., PhantomJS Authors 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.
 */

const Browser = require('../lib/Browser');
let browser = new Browser();

browser.newPage().then(async page => {
  await page.evaluateOnNewDocument(function() {
    Math.random = () => 42 / 100;
  });
  let result = await page.navigate('http://ariya.github.com/js/random/');
  if (result) {
    console.log(await page.evaluate(function() {
      return document.getElementById('numbers').textContent;
    }));
  } else {
    console.log('Network error.');
  }
  browser.close();
});