electron/docs/api/web-contents.md

webContents

webContents is an EventEmitter.

It is responsible for rendering and controlling a web page and is a property of the BrowserWindow object. An example of accessing the webContents object:

var BrowserWindow = require('browser-window');

var win = new BrowserWindow({width: 800, height: 1500});
win.loadUrl("http://github.com");

var webContents = win.webContents;

Events

The webContents object emits the following events:

Event: 'did-finish-load'

Emitted when the navigation is done, i.e. the spinner of the tab has stopped spinning, and the onload event was dispatched.

Event: 'did-fail-load'

Returns:

• event Event
• errorCode Integer
• errorDescription String
• validatedUrl String

This event is like did-finish-load but emitted when the load failed or was cancelled, e.g. window.stop() is invoked.

Event: 'did-frame-finish-load'

Returns:

• event Event
• isMainFrame Boolean

Emitted when a frame has done navigation.

Event: 'did-start-loading'

Corresponds to the points in time when the spinner of the tab started spinning.

Event: 'did-stop-loading'

Corresponds to the points in time when the spinner of the tab stopped spinning.

Event: 'did-get-response-details'

Returns:

• event Event
• status Boolean
• newUrl String
• originalUrl String
• httpResponseCode Integer
• requestMethod String
• referrer String
• headers Object

Emitted when details regarding a requested resource are available. status indicates the socket connection to download the resource.

Event: 'did-get-redirect-request'

Returns:

• event Event
• oldUrl String
• newUrl String
• isMainFrame Boolean
• httpResponseCode Integer
• requestMethod String
• referrer String
• headers Object

Emitted when a redirect is received while requesting a resource.

Event: 'dom-ready'

Returns:

• event Event

Emitted when the document in the given frame is loaded.

Event: 'page-favicon-updated'

Returns:

• event Event
• favicons Array - Array of Urls

Emitted when page receives favicon urls.

Event: 'new-window'

Returns:

• event Event
• url String
• frameName String
• disposition String - Can be default, foreground-tab, background-tab, new-window and other.
• options Object - The options which will be used for creating the new BrowserWindow.

Emitted when the page requests to open a new window for a url. It could be requested by window.open or an external link like <a target='_blank'>.

By default a new BrowserWindow will be created for the url.

Calling event.preventDefault() will prevent creating new windows.

Event: 'will-navigate'

Returns:

• event Event
• url String

Emitted when a user or the page wants to start navigation. It can happen when the window.location object is changed or a user clicks a link in the page.

This event will not emit when the navigation is started programmatically with APIs like webContents.loadUrl and webContents.back.

Calling event.preventDefault() will prevent the navigation.

Event: 'crashed'

Emitted when the renderer process has crashed.

Event: 'plugin-crashed'

Returns:

• event Event
• name String
• version String

Emitted when a plugin process has crashed.

Event: 'destroyed'

Emitted when webContents is destroyed.

Instance Methods

The webContents object has the following instance methods:

webContents.session

Returns the session object used by this webContents.

See session documentation for this object's methods.

webContents.loadUrl(url[, options])

• url URL
• options Object (optional), properties:
  • httpReferrer String - A HTTP Referrer url.
  • userAgent String - A user agent originating the request.

Loads the url in the window, the url must contain the protocol prefix, e.g. the http:// or file://.

webContents.getUrl()

var BrowserWindow = require('browser-window');

var win = new BrowserWindow({width: 800, height: 600});
win.loadUrl("http://github.com");

var currentUrl = win.webContents.getUrl();

Returns URL of the current web page.

webContents.getTitle()

Returns the title of the current web page.

webContents.isLoading()

Returns whether web page is still loading resources.

webContents.isWaitingForResponse()

Returns whether the web page is waiting for a first-response from the main resource of the page.

webContents.stop()

Stops any pending navigation.

webContents.reload()

Reloads the current web page.

webContents.reloadIgnoringCache()

Reloads current page and ignores cache.

webContents.canGoBack()

Returns whether the browser can go back to previous web page.

webContents.canGoForward()

Returns whether the browser can go forward to next web page.

webContents.canGoToOffset(offset)

• offset Integer

Returns whether the web page can go to offset.

webContents.clearHistory()

Clears the navigation history.

webContents.goBack()

Makes the browser go back a web page.

webContents.goForward()

Makes the browser go forward a web page.

webContents.goToIndex(index)

• index Integer

Navigates browser to the specified absolute web page index.

webContents.goToOffset(offset)

• offset Integer

Navigates to the specified offset from the "current entry".

webContents.isCrashed()

Whether the renderer process has crashed.

webContents.setUserAgent(userAgent)

• userAgent String

Overrides the user agent for this web page.

webContents.getUserAgent()

Returns a String representing the user agent for this web page.

webContents.insertCSS(css)

• css String

Injects CSS into the current web page.

webContents.executeJavaScript(code[, userGesture])

• code String
• userGesture Boolean (optional)

Evaluates code in page.

In the browser window some HTML APIs like requestFullScreen can only be invoked by a gesture from the user. Setting userGesture to true will remove this limitation.

webContents.setAudioMuted(muted)

• muted Boolean

Mute the audio on the current web page.

webContents.isAudioMuted()

Returns whether this page has been muted.

webContents.undo()

Executes the editing command undo in web page.

webContents.redo()

Executes the editing command redo in web page.

webContents.cut()

Executes the editing command cut in web page.

webContents.copy()

Executes the editing command copy in web page.

webContents.paste()

Executes the editing command paste in web page.

webContents.pasteAndMatchStyle()

Executes the editing command pasteAndMatchStyle in web page.

webContents.delete()

Executes the editing command delete in web page.

webContents.selectAll()

Executes the editing command selectAll in web page.

webContents.unselect()

Executes the editing command unselect in web page.

webContents.replace(text)

• text String

Executes the editing command replace in web page.

webContents.replaceMisspelling(text)

• text String

Executes the editing command replaceMisspelling in web page.

webContents.hasServiceWorker(callback)

• callback Function

Checks if any ServiceWorker is registered and returns a boolean as response to callback.

webContents.unregisterServiceWorker(callback)

• callback Function

Unregisters any ServiceWorker if present and returns a boolean as response to callback when the JS promise is fulfilled or false when the JS promise is rejected.

webContents.print([options])

options Object (optional), properties:

• silent Boolean - Don't ask user for print settings, defaults to false
• printBackground Boolean - Also prints the background color and image of the web page, defaults to false.

Prints window's web page. When silent is set to false, Electron will pick up system's default printer and default settings for printing.

Calling window.print() in web page is equivalent to calling webContents.print({silent: false, printBackground: false}).

Note: On Windows, the print API relies on pdf.dll. If your application doesn't need the print feature, you can safely remove pdf.dll to reduce binary size.

webContents.printToPDF(options, callback)

options Object, properties:

• marginsType Integer - Specify the type of margins to use
  • 0 - default
  • 1 - none
  • 2 - minimum
• pageSize String - Specify page size of the generated PDF.
  • A4
  • A3
  • Legal
  • Letter
  • Tabloid
• printBackground Boolean - Whether to print CSS backgrounds.
• printSelectionOnly Boolean - Whether to print selection only.
• landscape Boolean - true for landscape, false for portrait.

callback Function - function(error, data) {}

• error Error
• data Buffer - PDF file content.

Prints window's web page as PDF with Chromium's preview printing custom settings.

By default, an empty options will be regarded as:

{
  marginsType: 0,
  printBackground: false,
  printSelectionOnly: false,
  landscape: false
}

var BrowserWindow = require('browser-window');
var fs = require('fs');

var win = new BrowserWindow({width: 800, height: 600});
win.loadUrl("http://github.com");

win.webContents.on("did-finish-load", function() {
  // Use default printing options
  win.webContents.printToPDF({}, function(error, data) {
    if (error) throw error;
    fs.writeFile("/tmp/print.pdf", data, function(error) {
      if (error)
        throw error;
      console.log("Write PDF successfully.");
    })
  })
});

webContents.addWorkSpace(path)

• path String

Adds the specified path to DevTools workspace.

webContents.removeWorkSpace(path)

• path String

Removes the specified path from DevTools workspace.

webContents.send(channel[, args...])

• channel String
• args... (optional)

Send args... to the web page via channel in an asynchronous message, the web page can handle it by listening to the channel event of the ipc module.

An example of sending messages from the main process to the renderer process:

// In the main process.
var window = null;
app.on('ready', function() {
  window = new BrowserWindow({width: 800, height: 600});
  window.loadUrl('file://' + __dirname + '/index.html');
  window.webContents.on('did-finish-load', function() {
    window.webContents.send('ping', 'whoooooooh!');
  });
});

<!-- index.html -->
<html>
<body>
  <script>
    require('ipc').on('ping', function(message) {
      console.log(message);  // Prints "whoooooooh!"
    });
  </script>
</body>
</html>

Note:

1. The IPC message handler in web pages does not have an event parameter, which is different from the handlers in the main process.
2. There is no way to send synchronous messages from the main process to a renderer process, because it would be very easy to cause dead locks.

webContents.enableDeviceEmulation(parameters)

parameters Object, properties:

• screenPosition String - Specify the screen type to emulate (default: desktop)
  • desktop
  • mobile
• screenSize Object - Set the emulated screen size (screenPosition == mobile)
  • width Integer - Set the emulated screen width
  • height Integer - Set the emulated screen height
• viewPosition Object - Position the view on the screen (screenPosition == mobile) (default: {x: 0, y: 0})
  • x Integer - Set the x axis offset from top left corner
  • y Integer - Set the y axis offset from top left corner
• deviceScaleFactor Integer - Set the device scale factor (if zero defaults to original device scale factor) (default: 0)
• viewSize Object - Set the emulated view size (empty means no override)
  • width Integer - Set the emulated view width
  • height Integer - Set the emulated view height
• fitToView Boolean - Whether emulated view should be scaled down if necessary to fit into available space (default: false)
• offset Object - Offset of the emulated view inside available space (not in fit to view mode) (default: {x: 0, y: 0})
  • x Float - Set the x axis offset from top left corner
  • y Float - Set the y axis offset from top left corner
• scale Float - Scale of emulated view inside available space (not in fit to view mode) (default: 1)

Enable device emulation with the given parameters.

webContents.disableDeviceEmulation()

Disable device emulation enabled by webContents.enableDeviceEmulation.

webContents.sendInputEvent(event)

• event Object
  • type String (required) - The type of the event, can be mouseDown, mouseUp, mouseEnter, mouseLeave, contextMenu, mouseWheel, keyDown, keyUp, char.
  • modifiers Array - An array of modifiers of the event, can include shift, control, alt, meta, isKeypad, isAutoRepeat, leftButtonDown, middleButtonDown, rightButtonDown, capsLock, numLock, left, right.

Sends an input event to the page.

For keyboard events, the event object also have following properties:

• keyCode String (required) - A single character that will be sent as keyboard event. Can be any UTF-8 character.

For mouse events, the event object also have following properties:

• x Integer (required)
• y Integer (required)
• button String - The button pressed, can be left, middle, right
• globalX Integer
• globalY Integer
• movementX Integer
• movementY Integer
• clickCount Integer

For the mouseWheel event, the event object also have following properties:

• deltaX Integer
• deltaY Integer
• wheelTicksX Integer
• wheelTicksY Integer
• accelerationRatioX Integer
• accelerationRatioY Integer
• hasPreciseScrollingDeltas Boolean
• canScroll Boolean

webContents.beginFrameSubscription(callback)

• callback Function

Begin subscribing for presentation events and captured frames, the callback will be called with callback(frameBuffer) when there is a presentation event.

The frameBuffer is a Buffer that contains raw pixel data. On most machines, the pixel data is effectively stored in 32bit BGRA format, but the actual representation depends on the endianness of the processor (most modern processors are little-endian, on machines with big-endian processors the data is in 32bit ARGB format).

webContents.endFrameSubscription()

End subscribing for frame presentation events.