simple-headless-chrome/build/util.js

Headless Chrome abstraction to simplify the interaction with the browser. It may be used for crawling sites, test automation, etc

'use strict';

var cssesc = require('cssesc');

/**
 * Checks if the browser is initialized. Exits the process if it's not
 */
exports.browserIsInitialized = function browserIsInitialized() {
  if (!this.isInitialized()) {
    console.error('HeadlessChrome is not ready; call browser.init() before requesting other actions');
    process.exit(1);
  }
};

/**
 * As the selectors may contain colons, it's necessary to escape them in order to correctly match an element
 * @param {string} selector - The selector string
 * @return {string} - The selector with colons escaped (One backslash to escape the ':' for CSS, and other to escape the first one for JS)
 */
exports.fixSelector = function fixSelector(selector) {
  return cssesc(selector);
};

/**
 * Creates some delay
 * @param {number} delay - Delay in miliseconds
 * @return {promise} - The promise that will solve after the delay
 */
var sleep = exports.sleep = function (delay) {
  return new Promise(function (resolve) {
    return setTimeout(resolve, delay);
  });
};

/**
 * Runs a promise and throws an error if it's not resolved before the timeout
 * @param {promise} promise - The promise to run
 * @param {number} timeout - The timeout time, in ms
 */
exports.promiseTimeout = function (promise, timeout) {
  // https://stackoverflow.com/questions/30936824/what-is-the-best-general-practice-to-timeout-a-function-in-promise
  // Handles the timeout internally, clearing it when the promise resolves.
  // It prevents the library to hang until the timeout is resolved
  var timer = null;

  return Promise.race([new Promise(function (resolve, reject) {
    timer = setTimeout(function () {
      var err = new Error('[Headless Chrome] Timeout after ' + timeout + ' ms');
      err.code = 'TIMEOUT';
      throw err;
    }, timeout);
    return timer;
  }), promise.then(function (value) {
    clearTimeout(timer);
    return value;
  })]);
};

/**
 * Transforms an interleave array into a key - value object
 * @param {array} interleaveArray - The interleave array
 * @return {object} - The key value object
 */
exports.interleaveArrayToObject = function (interleaveArray) {
  var attributes = {};
  for (var i = 0; i < interleaveArray.length; i++) {
    var key = interleaveArray[i];
    var value = interleaveArray[++i];
    attributes[key] = value;
  }
  return attributes;
};

/**
 * Given an object, transforms it's properties to a URL encoded string
 * @param {object} object - The object to transform
 * @return {string} - The URL Enconded object
 */
exports.objectToEncodedUri = function (object) {
  var encodedString = '';
  for (var prop in object) {
    if (object.hasOwnProperty(prop)) {
      if (encodedString.length > 0) {
        encodedString += '&';
      }
      encodedString += encodeURI(prop + '=' + object[prop]);
    }
  }
  return encodedString;
};