lighthouse/gatherers/viewport.js

> Stops you crashing into the rocks; lights the way

/**
 * @license
 * Copyright 2016 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.
 */
'use strict';

const Gather = require('./gather');

class Viewport extends Gather {

  /**
   * @param {!{driver: !Object}} options Run options
   * @return {!Promise<{viewport: !string}>} The value of the viewport meta's content attribute, or null
   */
  afterPageLoad(options) {
    const driver = options.driver;

    return driver.querySelector('head meta[name="viewport"]')
      .then(node => node && node.getAttribute('content'))
      .then(viewport => {
        this.artifact = {viewport};
      });
  }
}

module.exports = Viewport;