chrome-remote-interface

Chrome Remote Debugging Protocol interface

chrome-remote-interface

Remote Debugging Protocol interface that helps to instrument Chrome by providing a simple abstraction of the two main objects exposed by the protocol in a Node.js fashion: commands and notifications.

chrome-remote-interface is listed among third-party Chrome debugging protocol clients.

npm install chrome-remote-interface

Chrome needs to be started with the --remote-debugging-port=<port> option to enable the Remote Debugging Protocol, for example:

google-chrome --remote-debugging-port=9222

The following snippet loads https://github.com and dumps every request made.

var Chrome = require('chrome-remote-interface');
Chrome(function (chrome) {
    with (chrome) {
        Network.requestWillBeSent(function (params) {
            console.log(params.request.url);
        });
        Page.loadEventFired(close);
        Network.enable();
        Page.enable();
        once('ready', function () {
            Page.navigate({'url': 'https://github.com'});
        });
    }
}).on('error', function () {
    console.error('Cannot connect to Chrome');
});

This module comes with a REPL interface that can be used to interactively control Chrome (run with --help to display the list of available options). It supports command execution and event binding, see the documentation for chrome.<domain>.<method>([params], [callback]) and chrome.<domain>.<event>(callback). Here's a sample session:

chrome> Network.enable()
chrome> Network.requestWillBeSent(console.log)
chrome> Page.navigate({url: 'https://github.com'})

Using the provided help field it's possible to obtain information on the events and methods available through the Remote Debugging Protocol. For example to learn how to call Page.navigate type:

chrome> Page.navigate.help
{ type: 'command',
  name: 'navigate',
  parameters:
   [ { name: 'url',
       type: 'string',
       description: 'URL to navigate the page to.' } ],
  returns:
   [ { name: 'frameId',
       '$ref': 'FrameId',
       hidden: true,
       description: 'Frame id that will be navigated.' } ],
  description: 'Navigates current page to the given URL.',
  handlers: [ 'browser', 'renderer' ] }

The type field determines whether this member is a command or an event.

For what concerns the types instead (they usually start with an upper case letter), just type its name:

chrome> Network.Timestamp
{ id: 'Timestamp',
  type: 'number',
  description: 'Number of seconds since epoch.' }

Currently it is not possible to fetch the protocol descriptor (protocol.json) directly from the instrumented Chrome instance (see #10); rather, that file can be fetched from the proper source repository at every connection. By default, the hardcoded local version is used.

To override the above behavior there are basically three options:

  1. update the local copy with make update-protocol;

  2. pass a custom protocol descriptor (use null to fetch it from the remote repository) upon connection;

  3. use the raw version of the commands and events interface.

Connects to a remote instance of Chrome using the Remote Debugging Protocol.

options is an object with the following optional properties:

  • host: Remote Debugging Protocol host. Defaults to localhost;
  • port: Remote Debugging Protocol port. Defaults to 9222;
  • chooseTab: Either a callback or a tab object (i.e. those returned by New and List methods). The callback is used to determine which remote tab attach to, it takes the array returned by the List method and must return the numeric index of a tab. Defaults to a function which returns the currently active tab (function (tabs) { return 0; }).
  • protocol: Remote Debugging Protocol descriptor object. Passing null causes the proper protocol descriptor to be fetched from the remote Chrome repository according to the version exposed by the instrumented Chrome instance, falling back to the default if that is not possible. Defaults to the hardcoded local version.

callback is a listener automatically added to the connect event of the returned EventEmitter.

Returns an EventEmitter that supports the following events:

function (chrome) {}

Emitted when the connection to Chrome is established.

chrome is an instance of the Chrome class.

function (err) {}

Emitted if http://host:port/json can't be reached or if it's not possible to connect to Chrome's remote debugging WebSocket.

err is an instance of Error.

Fetch the Remote Debugging Protocol descriptor from the Chrome repository according to the version of the remote Chrome instance, or fall back to the local hardcoded version if not available.

options is an object with the following optional properties:

callback is executed when the protocol is fetched, it gets the following arguments:

  • err: a Error object indicating the success status;
  • fromChrome: a boolean indicating whether the protocol has been fetched from the Chrome repository or not;
  • protocol: the Remote Debugging Protocol descriptor.

For example:

var Chrome = require('chrome-remote-interface');
Chrome.Protocol(function (errfromChromeprotocol) {
    if (!err) {
        console.log(JSON.stringify(protocol, null, 4));
    }
});

Request the list of the available open tabs of the remote Chrome instance.

options is an object with the following optional properties:

callback is executed when the list is correctly received, it gets the following arguments:

  • err: a Error object indicating the success status;
  • tabs: the array returned by http://host:port/json/list containing the tab list.

For example:

var Chrome = require('chrome-remote-interface');
Chrome.List(function (errtabs) {
    if (!err) {
        console.log(tabs);
    }
});

Create a new tab in the remote Chrome instance.

options is an object with the following optional properties:

callback is executed when the tab is created, it gets the following arguments:

  • err: a Error object indicating the success status;
  • tab: the object returned by http://host:port/json/new containing the tab.

For example:

var Chrome = require('chrome-remote-interface');
Chrome.New(function (errtab) {
    if (!err) {
        console.log(tab);
    }
});

Activate an open tab of the remote Chrome instance.

options is an object with the following properties:

callback is executed when the response to the activation request is received. It gets the following arguments:

  • err: a Error object indicating the success status;

For example:

var Chrome = require('chrome-remote-interface');
Chrome.Activate({'id': 'CC46FBFA-3BDA-493B-B2E4-2BE6EB0D97EC'}, function (err) {
    if (!err) {
        console.log('success! tab is closing');
    }
});

Close an open tab of the remote Chrome instance.

options is an object with the following properties:

callback is executed when the response to the close request is received. It gets the following arguments:

  • err: a Error object indicating the success status;

For example:

var Chrome = require('chrome-remote-interface');
Chrome.Close({'id': 'CC46FBFA-3BDA-493B-B2E4-2BE6EB0D97EC'}, function (err) {
    if (!err) {
        console.log('success! tab is closing');
    }
});

Note that the callback is fired when the tab is queued for removal, but the actual removal will occur asynchronously. It typically takes ~200ms for this to occur.

Request version information from the remote Chrome instance.

options is an object with the following optional properties:

callback is executed when the version information is correctly received, it gets the following arguments:

  • err: a Error object indicating the success status;
  • info: a JSON object returned by http://host:port/json/version containing the version information.

For example:

var Chrome = require('chrome-remote-interface');
Chrome.Version(function (errinfo) {
    if (!err) {
        console.log(info);
    }
});
function (message) {}

Emitted when Chrome sends a notification through the WebSocket.

message is the object received, it has the following properties:

  • method: a string describing the notification (e.g., 'Network.requestWillBeSent').
  • params: an object containing the payload.

Refer to the Remote Debugging Protocol specifications for more information.

For example:

on('event', function (message) {
    if (message.method === 'Network.requestWillBeSent') {
        console.log(message.params);
    }
});
function (params) {}

Emitted when Chrome sends a notification for <method> through the WebSocket.

params is an object containing the payload.

This is just a utility event which allows to easily listen for specific notifications (see the above event), for example:

chrome.on('Network.requestWillBeSent', console.log);
function () {}

Emitted every time that there are no more pending commands waiting for a response from Chrome. Note that the interaction with Chrome is asynchronous so the only way to serialize a sequence of commands is to use the callback provided by the chrome.send method. This event acts as a barrier and it is useful to avoid the callback hell in certain simple situations.

For example to load a URL only after having enabled the notifications of both Network and Page domains:

Network.enable();
Page.enable();
once('ready', function() {
    Page.navigate({'url': 'https://github.com'});
});

In this particular case, not enforcing this kind of serialization may cause that Chrome doesn't properly deliver the desired notifications the client.

Issue a command to Chrome.

method is a string describing the command.

params is an object containing the payload.

callback is executed when Chrome sends a response to this command, it gets the following arguments:

  • error: a boolean value indicating the success status, as reported by Chrome;
  • response: an object containing either the response sent from Chrome (result field, if error === false) or the indication of the error (error field, if error === true).

Note that the field id mentioned in the Remote Debugging Protocol specifications is managed internally and it's not exposed to the user.

For example:

chrome.send('Page.navigate', {'url': 'https://github.com'}, console.log);

Just a shorthand for:

chrome.send('<domain>.<method>', params, callback);

For example:

chrome.Page.navigate({'url': 'https://github.com'}, console.log);

Just a shorthand for:

chrome.on('<domain>.<event>', callback);

For example:

chrome.Network.requestWillBeSent(console.log);

Close the connection to Chrome.