jsdom

What is jsdom?

The jsdom npm package is a pure-JavaScript implementation of many web standards, notably the WHATWG DOM and HTML Standards, for use with Node.js. It is designed to create a web browsing environment similar to what you would find in a web browser, allowing for the parsing and manipulation of HTML and XML documents. It can be used for testing web pages and JavaScript libraries in a Node.js environment.

What are jsdom's main functionalities?

DOM Manipulation

This feature allows you to manipulate the DOM of a document. The code sample demonstrates how to append a new list item to an unordered list.

const { JSDOM } = require('jsdom');
const dom = new JSDOM(`<ul><li>Item 1</li></ul>`);
const ul = dom.window.document.querySelector('ul');
ul.appendChild(dom.window.document.createElement('li')).textContent = 'Item 2';
console.log(dom.window.document.body.innerHTML);

Event Handling

This feature enables you to simulate and handle events. The code sample shows how to simulate a click event on a button and handle it by logging a message.

const { JSDOM } = require('jsdom');
const dom = new JSDOM(`<button id='myButton'>Click me</button>`);
const button = dom.window.document.querySelector('#myButton');
button.addEventListener('click', () => console.log('Button clicked!'));
button.click();

Fetching Remote Content

This feature allows you to fetch remote content and create a JSDOM instance from it. The code sample demonstrates fetching and logging the HTML content of a webpage.

const { JSDOM } = require('jsdom');
JSDOM.fromURL('https://example.com/').then(dom => {
  console.log(dom.serialize());
});

Running Scripts

This feature allows you to run scripts within the context of the JSDOM instance. The code sample shows how to execute a script that changes the text content of the document body.

const { JSDOM } = require('jsdom');
const dom = new JSDOM(`<script>document.body.textContent = 'Hello, world!';</script>`);
console.log(dom.window.document.body.textContent);

Other packages similar to jsdom

cheerio

Cheerio is a fast, flexible, and lean implementation of core jQuery designed specifically for the server. It does not implement a full web browser API as jsdom does, but it is often used for simpler DOM manipulation tasks and is faster due to its focus on a subset of use cases.

puppeteer

Puppeteer is a Node library which provides a high-level API to control Chrome or Chromium over the DevTools Protocol. It is more powerful for tasks like web scraping, automated testing, and rendering since it operates over a real browser, but it is heavier and more resource-intensive compared to jsdom.

phantomjs

PhantomJS is a headless WebKit scriptable with a JavaScript API. It has similar capabilities to Puppeteer but uses WebKit as the rendering engine instead of Chromium. It is no longer actively maintained, but it was once a popular choice for headless website testing.

README

jsdom

A JavaScript implementation of the W3C DOM.

Install

$ npm install jsdom

If this gives you trouble with errors about installing Contextify, especially on Windows, see below.

Human contact

see: mailing list

Easymode

Bootstrapping a DOM is generally a difficult process involving many error prone steps. We didn't want jsdom to fall into the same trap and that is why a new method, jsdom.env(), has been added in jsdom 0.2.0 which should make everyone's lives easier.

with URL

// Count all of the links from the nodejs build page
var jsdom = require("jsdom");

jsdom.env(
  "http://nodejs.org/dist/",
  ["http://code.jquery.com/jquery.js"],
  function (errors, window) {
    console.log("there have been", window.$("a").length, "nodejs releases!");
  }
);

or with raw HTML

// Run some jQuery on a html fragment
var jsdom = require("jsdom");

jsdom.env(
  '<p><a class="the-link" href="https://github.com/tmpvar/jsdom">jsdom\'s Homepage</a></p>',
  ["http://code.jquery.com/jquery.js"],
  function(errors, window) {
    console.log("contents of a.the-link:", window.$("a.the-link").text());
  }
);

or with a configuration object

// Print all of the news items on hackernews
var jsdom = require("jsdom");

jsdom.env({
  html: "http://news.ycombinator.com/",
  scripts: ["http://code.jquery.com/jquery.js"],
  done: function (errors, window) {
    var $ = window.$;
    console.log("HN Links");
    $("td.title:not(:last) a").each(function() {
      console.log(" -", $(this).text());
    });
  }
});

or with raw JavaScript source

// Print all of the news items on hackernews
var jsdom = require("jsdom");
var fs = require("fs");
var jquery = fs.readFileSync("./jquery.js").toString();

jsdom.env({
  html: "http://news.ycombinator.com/",
  src: [jquery],
  done: function (errors, window) {
    var $ = window.$;
    console.log("HN Links");
    $("td.title:not(:last) a").each(function() {
      console.log(" -", $(this).text());
    });
  }
});

How it works

jsdom.env is built for ease of use, which is rare in the world of the DOM! Since the web has some absolutely horrible JavaScript on it, as of jsdom 0.2.0 jsdom.env will not process external resources (scripts, images, etc). If you want to process the JavaScript use one of the methods below (jsdom.jsdom or jsdom.jQueryify)

jsdom.env(html, [scripts], [config], callback);

• html (required): may be a URL, HTML fragment, or file.
• scripts (optional): may contain files or URLs.
• config (optional): see below.
• callback (required): takes two arguments:
  • errors: an array of errors
  • window: a brand new window

example:

jsdom.env(html, function (errors, window) {
  // free memory associated with the window
  window.close();
});

If you would like to specify a configuration object only:

jsdom.env(config);

• config.html: see html above.
• config.scripts: see scripts above.
• config.url: the URL for location.href if config.html is not a file path or URL. (Relative <a href> and <img src> values are evaluated relative to this.)
• config.src: an array of JavaScript strings that will be evaluated against the resulting document. Similar to scripts, but it accepts JavaScript instead of paths/URLs.
• config.done: see callback above.
• config.document:
  • referer: the new document will have this referer
  • cookie: manually set a cookie value, e.g. 'key=value; expires=Wed, Sep 21 2011 12:00:00 GMT; path=/'
• config.features : see Flexibility section below. Note: the default feature set for jsdom.env does not include fetching remote JavaScript and executing it. This is something that you will need to carefully enable yourself.

For the hardcore

If you want to spawn a document/window and specify all sorts of options this is the section for you. This section covers the jsdom.jsdom method:

var jsdom = require("jsdom").jsdom;
var doc = jsdom(markup, level, options);
var window = doc.createWindow();

• markup is an HTML/XML document to be parsed. You can also pass null or an undefined value to get a basic document with empty <head> and <body> tags. Document fragments are also supported (including ""), and will behave as sanely as possible (e.g. the resulting document will lack the head, body and documentElement properties if the corresponding elements aren't included).

• level is null (which means level3) by default, but you can pass another level if you'd like.

  var jsdom = require("jsdom");
  var doc = jsdom.jsdom("<html><body></body></html>", jsdom.level(1, "core"));
  

• options see the Flexibility section below.

Flexibility

One of the goals of jsdom is to be as minimal and light as possible. This section details how someone can change the behavior of Documents on the fly. These features are baked into the DOMImplementation that every Document has, and may be tweaked in two ways:

1. When you create a new Document using the jsdom builder (require("jsdom").jsdom())

var jsdom = require("jsdom").jsdom;
var doc = jsdom("<html><body></body></html>", null, {
    features: {
      FetchExternalResources : ["img"]
    }
});

Do note, that this will only affect the document that is currently being created. All other documents will use the defaults specified below (see: Default Features).

1. Before creating any documents, you can modify the defaults for all future documents:

require("jsdom").defaultDocumentFeatures = {
    FetchExternalResources: ["script"],
    ProcessExternalResources: false
};

Default Features

Default features are extremely important for jsdom as they lower the configuration requirement and present developers a set of consistent default behaviors. The following sections detail the available features, their defaults, and the values that jsdom uses.

FetchExternalResources

• Default: ["script"]
• Allowed: ["script", "img", "css", "frame", "iframe", "link"] or false

Enables/disables fetching files over the file system/HTTP.

ProcessExternalResources

• Default: ["script"]
• Allowed: ["script"] or false

Disabling this will disable script execution (currently only JavaScript).

SkipExternalResources

• Default: false
• Allowed: /url to be skipped/ or false
• Example: /http:\/\/example.org/js/bad\.js/

Do not download and process resources with url matching a regular expression.

Canvas

jsdom includes support for using the canvas package to extend any <canvas> elements with the canvas API. To make this work, you need to include canvas as a dependency in your project, as a peer of jsdom. If jsdom can find the canvas package, it will use it, but if it's not present, then <canvas> elements will behave like <div>s.

More Examples

Creating a document-less window

var jsdom = require("jsdom");
var window = jsdom.createWindow();

console.log(window.document); // output: undefined

Creating a document

var jsdom = require("jsdom");
var doc = new (jsdom.level(1, "core").Document)();

console.log(doc.nodeName); // outputs: #document

Creating a browser-like BOM/DOM/Window

var jsdom = require("jsdom").jsdom;
var document = jsdom("<html><head></head><body>hello world</body></html>");
var window = document.createWindow();

console.log(window.document.innerHTML);
// output: "<html><head></head><body>hello world</body></html>"

console.log(window.innerWidth);
// output: 1024

console.log(typeof window.document.getElementsByClassName);
// outputs: function

jQueryify

var jsdom = require("jsdom");
var window = jsdom.jsdom().createWindow();

jsdom.jQueryify(window, "http://code.jquery.com/jquery.js", function () {
  window.$("body").append('<div class="testing">Hello World, It works</div>');

  console.log(window.$(".testing").text());
});

Passing objects to scripts inside the page

var jsdom = require("jsdom").jsdom;
var window = jsdom().createWindow();

window.__myObject = { foo: "bar" };

var scriptEl = window.document.createElement("script");
scriptEl.src = "anotherScript.js";
window.document.body.appendChild(scriptEl);

// anotherScript.js will have the ability to read `window.__myObject`, even
// though it originated in Node!

Test Compliance:

 level1/core                        535/535      100%
 level1/html                        238/238      100%
 level1/svg                         527/527      100%
 level2/core                        283/283      100%
 level2/html                        706/706      100%
 level2/style                         15/15      100%
 level2/extra                           4/4      100%
 level2/events                        24/24      100%
 level3/xpath                         93/93      100%
 window/index                           5/5      100%
 window/script                        10/10      100%
 window/frame                         16/16      100%
 sizzle/index                         14/14      100%
 jsdom/index                          89/89      100%
 jsdom/parsing                          8/8      100%
 jsonp/jsonp                            1/1      100%
 browser/contextifyReplacement          4/4      100%
 browser/index                        34/34      100%
------------------------------------------------------
TOTALS: 0/2606 failed; 100% success

Running the tests

First you'll want to npm install. To run all the tests, use npm test, which just calls node test/runner.

Using test/runner directly, you can slice and dice which tests your want to run from different levels. Usage is as follows:

test/runner --help
Run the jsdom test suite

Options:
-s, --suites     suites that you want to run. ie: -s level1/core,1/html,html [string]
-f, --fail-fast  stop on the first failed test
-h, --help       show the help
-t, --tests      choose the test cases to run. ie: -t jquery

Contextify

Contextify is a dependency of jsdom, used for running <script> tags within the page. In other words, it allows jsdom, which is run in Node.js, to run strings of JavaScript in an isolated environment that pretends to be a browser environment instead of a server. You can see how this is an important feature.

Unfortunately, doing this kind of magic requires C++. And in Node.js, using C++ from JavaScript means using "native modules." Native modules are compiled at installation time so that they work precisely for your machine; that is, you don't download a contextify binary from npm, but instead build one locally after downloading the source from npm.

For Mac and Linux users, this is usually fine. Their systems come preinstalled with the necessaries for compiling C++. For Windows users, however, things can be tricky. Thus, one of the most common problems with jsdom is trying to use it on Windows without the proper compilation tools installed. Here's what you need to compile Contextify, and thus to install jsdom, on Windows:

• A recent copy of the x86 version of Node.js for Windows, not the x64 version.
• A copy of Visual C++ 2010 Express.
• A copy of Python 2.7, installed in the default location of C:\Python27.

There are some slight modifications to this that can work; for example full versions of Visual Studio usually work, and sometimes you can even get an x64 version of Node.js working too. But it's tricky, so start with the basics!