electron/docs/api/web-contents.md

webContents

Render and control web pages.

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:

const {BrowserWindow} = require('electron');

let win = new BrowserWindow({width: 800, height: 1500});
win.loadURL('http://github.com');

let contents = win.webContents;

Methods

These methods can be accessed from the webContents module:

const {webContents} = require('electron');

webContents.getAllWebContents()

Returns an array of all web contents. This will contain web contents for all windows, webviews, opened devtools, and devtools extension background pages.

webContents.getFocusedWebContents()

Returns the web contents that is focused in this application, otherwise returns null.

Class: WebContents

Instance 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
• isMainFrame Boolean

This event is like did-finish-load but emitted when the load failed or was cancelled, e.g. window.stop() is invoked. The full list of error codes and their meaning is available here. Note that redirect responses will emit errorCode -3; you may want to ignore that error explicitly.

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
• resourceType String

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.

It is also not emitted for in-page navigations, such as clicking anchor links or updating the window.location.hash. Use did-navigate-in-page event for this purpose.

Calling event.preventDefault() will prevent the navigation.

Event: 'did-navigate'

Returns:

• event Event
• url String

Emitted when a navigation is done.

This event is not emitted for in-page navigations, such as clicking anchor links or updating the window.location.hash. Use did-navigate-in-page event for this purpose.

Event: 'did-navigate-in-page'

Returns:

• event Event
• url String

Emitted when an in-page navigation happened.

When in-page navigation happens, the page URL changes but does not cause navigation outside of the page. Examples of this occurring are when anchor links are clicked or when the DOM hashchange event is triggered.

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.

Event: 'devtools-opened'

Emitted when DevTools is opened.

Event: 'devtools-closed'

Emitted when DevTools is closed.

Event: 'devtools-focused'

Emitted when DevTools is focused / opened.

Event: 'certificate-error'

Returns:

• event Event
• url URL
• error String - The error code
• certificate Object
  • data Buffer - PEM encoded data
  • issuerName String - Issuer's Common Name
  • subjectName String - Subject's Common Name
  • serialNumber String - Hex value represented string
  • validStart Integer - Start date of the certificate being valid in seconds
  • validExpiry Integer - End date of the certificate being valid in seconds
  • fingerprint String - Fingerprint of the certificate
• callback Function

Emitted when failed to verify the certificate for url.

The usage is the same with the certificate-error event of app.

Event: 'select-client-certificate'

Returns:

• event Event
• url URL
• certificateList [Objects]
  • data Buffer - PEM encoded data
  • issuerName String - Issuer's Common Name
  • subjectName String - Subject's Common Name
  • serialNumber String - Hex value represented string
  • validStart Integer - Start date of the certificate being valid in seconds
  • validExpiry Integer - End date of the certificate being valid in seconds
  • fingerprint String - Fingerprint of the certificate
• callback Function

Emitted when a client certificate is requested.

The usage is the same with the select-client-certificate event of app.

Event: 'login'

Returns:

• event Event
• request Object
  • method String
  • url URL
  • referrer URL
• authInfo Object
  • isProxy Boolean
  • scheme String
  • host String
  • port Integer
  • realm String
• callback Function

Emitted when webContents wants to do basic auth.

The usage is the same with the login event of app.

Event: 'found-in-page'

Returns:

• event Event
• result Object
  • requestId Integer
  • finalUpdate Boolean - Indicates if more responses are to follow.
  • activeMatchOrdinal Integer (optional) - Position of the active match.
  • matches Integer (optional) - Number of Matches.
  • selectionArea Object (optional) - Coordinates of first match region.

Emitted when a result is available for webContents.findInPage request.

Event: 'media-started-playing'

Emitted when media starts playing.

Event: 'media-paused'

Emitted when media is paused or done playing.

Event: 'did-change-theme-color'

Emitted when a page's theme color changes. This is usually due to encountering a meta tag:

<meta name='theme-color' content='#ff0000'>

Event: 'update-target-url'

Returns:

• event Event
• url String

Emitted when mouse moves over a link or the keyboard moves the focus to a link.

Event: 'cursor-changed'

Returns:

• event Event
• type String
• image NativeImage (optional)
• scale Float (optional)

Emitted when the cursor's type changes. The type parameter can be default, crosshair, pointer, text, wait, help, e-resize, n-resize, ne-resize, nw-resize, s-resize, se-resize, sw-resize, w-resize, ns-resize, ew-resize, nesw-resize, nwse-resize, col-resize, row-resize, m-panning, e-panning, n-panning, ne-panning, nw-panning, s-panning, se-panning, sw-panning, w-panning, move, vertical-text, cell, context-menu, alias, progress, nodrop, copy, none, not-allowed, zoom-in, zoom-out, grab, grabbing, custom.

If the type parameter is custom, the image parameter will hold the custom cursor image in a NativeImage, and the scale will hold scaling information for the image.

Event: 'context-menu'

Returns:

• event Event
• params Object
  • x Integer - x coordinate
  • y Integer - y coordinate
  • linkURL String - URL of the link that encloses the node the context menu was invoked on.
  • linkText String - Text associated with the link. May be an empty string if the contents of the link are an image.
  • pageURL String - URL of the top level page that the context menu was invoked on.
  • frameURL String - URL of the subframe that the context menu was invoked on.
  • srcURL String - Source URL for the element that the context menu was invoked on. Elements with source URLs are images, audio and video.
  • mediaType String - Type of the node the context menu was invoked on. Can be none, image, audio, video, canvas, file or plugin.
  • hasImageContent Boolean - Whether the context menu was invoked on an image which has non-empty contents.
  • isEditable Boolean - Whether the context is editable.
  • selectionText String - Text of the selection that the context menu was invoked on.
  • titleText String - Title or alt text of the selection that the context was invoked on.
  • misspelledWord String - The misspelled word under the cursor, if any.
  • frameCharset String - The character encoding of the frame on which the menu was invoked.
  • inputFieldType String - If the context menu was invoked on an input field, the type of that field. Possible values are none, plainText, password, other.
  • menuSourceType String - Input source that invoked the context menu. Can be none, mouse, keyboard, touch, touchMenu.
  • mediaFlags Object - The flags for the media element the context menu was invoked on. See more about this below.
  • editFlags Object - These flags indicate whether the renderer believes it is able to perform the corresponding action. See more about this below.

The mediaFlags is an object with the following properties:

• inError Boolean - Whether the media element has crashed.
• isPaused Boolean - Whether the media element is paused.
• isMuted Boolean - Whether the media element is muted.
• hasAudio Boolean - Whether the media element has audio.
• isLooping Boolean - Whether the media element is looping.
• isControlsVisible Boolean - Whether the media element's controls are visible.
• canToggleControls Boolean - Whether the media element's controls are toggleable.
• canRotate Boolean - Whether the media element can be rotated.

The editFlags is an object with the following properties:

• canUndo Boolean - Whether the renderer believes it can undo.
• canRedo Boolean - Whether the renderer believes it can redo.
• canCut Boolean - Whether the renderer believes it can cut.
• canCopy Boolean - Whether the renderer believes it can copy
• canPaste Boolean - Whether the renderer believes it can paste.
• canDelete Boolean - Whether the renderer believes it can delete.
• canSelectAll Boolean - Whether the renderer believes it can select all.

Emitted when there is a new context menu that needs to be handled.

Event: 'select-bluetooth-device'

Returns:

• event Event
• devices [Objects]
  • deviceName String
  • deviceId String
• callback Function
  • deviceId String

Emitted when bluetooth device needs to be selected on call to navigator.bluetooth.requestDevice. To use navigator.bluetooth api webBluetooth should be enabled. If event.preventDefault is not called, first available device will be selected. callback should be called with deviceId to be selected, passing empty string to callback will cancel the request.

app.commandLine.appendSwitch('enable-web-bluetooth')

app.on('ready', () => {
  webContents.on('select-bluetooth-device', (event, deviceList, callback) => {
    event.preventDefault()
    let result = deviceList.find((device) => {
      return device.deviceName === 'test'
    })
    if (!result) {
      callback('')
    } else {
      callback(result.deviceId)
    }
  })
})

Instance Methods

contents.loadURL(url[, options])

• url URL
• options Object (optional)
  • httpReferrer String - A HTTP Referrer url.
  • userAgent String - A user agent originating the request.
  • extraHeaders String - Extra headers separated by "\n"

Loads the url in the window, the url must contain the protocol prefix, e.g. the http:// or file://. If the load should bypass http cache then use the pragma header to achieve it.

const options = {extraHeaders: 'pragma: no-cache\n'};
webContents.loadURL(url, options);

contents.downloadURL(url)

• url URL

Initiates a download of the resource at url without navigating. The will-download event of session will be triggered.

contents.getURL()

Returns URL of the current web page.

let win = new BrowserWindow({width: 800, height: 600});
win.loadURL('http://github.com');

let currentURL = win.webContents.getURL();

contents.getTitle()

Returns the title of the current web page.

contents.isFocused()

Returns a Boolean, whether the web page is focused.

contents.isLoading()

Returns whether web page is still loading resources.

contents.isLoadingMainFrame()

Returns whether the main frame (and not just iframes or frames within it) is still loading.

contents.isWaitingForResponse()

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

contents.stop()

Stops any pending navigation.

contents.reload()

Reloads the current web page.

contents.reloadIgnoringCache()

Reloads current page and ignores cache.

contents.canGoBack()

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

contents.canGoForward()

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

contents.canGoToOffset(offset)

• offset Integer

Returns whether the web page can go to offset.

contents.clearHistory()

Clears the navigation history.

contents.goBack()

Makes the browser go back a web page.

contents.goForward()

Makes the browser go forward a web page.

contents.goToIndex(index)

• index Integer

Navigates browser to the specified absolute web page index.

contents.goToOffset(offset)

• offset Integer

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

contents.isCrashed()

Whether the renderer process has crashed.

contents.setUserAgent(userAgent)

• userAgent String

Overrides the user agent for this web page.

contents.getUserAgent()

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

contents.insertCSS(css)

• css String

Injects CSS into the current web page.

contents.executeJavaScript(code[, userGesture, callback])

• code String
• userGesture Boolean (optional)
• callback Function (optional) - Called after script has been executed.
  • result

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.

contents.setAudioMuted(muted)

• muted Boolean

Mute the audio on the current web page.

contents.isAudioMuted()

Returns whether this page has been muted.

contents.undo()

Executes the editing command undo in web page.

contents.redo()

Executes the editing command redo in web page.

contents.cut()

Executes the editing command cut in web page.

contents.copy()

Executes the editing command copy in web page.

contents.paste()

Executes the editing command paste in web page.

contents.pasteAndMatchStyle()

Executes the editing command pasteAndMatchStyle in web page.

contents.delete()

Executes the editing command delete in web page.

contents.selectAll()

Executes the editing command selectAll in web page.

contents.unselect()

Executes the editing command unselect in web page.

contents.replace(text)

• text String

Executes the editing command replace in web page.

contents.replaceMisspelling(text)

• text String

Executes the editing command replaceMisspelling in web page.

contents.insertText(text)

• text String

Inserts text to the focused element.

contents.findInPage(text[, options])

• text String - Content to be searched, must not be empty.
• options Object (optional)
  • forward Boolean - Whether to search forward or backward, defaults to true.
  • findNext Boolean - Whether the operation is first request or a follow up, defaults to false.
  • matchCase Boolean - Whether search should be case-sensitive, defaults to false.
  • wordStart Boolean - Whether to look only at the start of words. defaults to false.
  • medialCapitalAsWordStart Boolean - When combined with wordStart, accepts a match in the middle of a word if the match begins with an uppercase letter followed by a lowercase or non-letter. Accepts several other intra-word matches, defaults to false.

Starts a request to find all matches for the text in the web page and returns an Integer representing the request id used for the request. The result of the request can be obtained by subscribing to found-in-page event.

contents.stopFindInPage(action)

• action String - Specifies the action to take place when ending webContents.findInPage request.
  • clearSelection - Clear the selection.
  • keepSelection - Translate the selection into a normal selection.
  • activateSelection - Focus and click the selection node.

Stops any findInPage request for the webContents with the provided action.

webContents.on('found-in-page', (event, result) => {
  if (result.finalUpdate)
    webContents.stopFindInPage('clearSelection');
});

const requestId = webContents.findInPage('api');

contents.capturePage([rect, ]callback)

• rect Object (optional) - The area of the page to be captured
  • x Integer
  • y Integer
  • width Integer
  • height Integer
• callback Function

Captures a snapshot of the page within rect. Upon completion callback will be called with callback(image). The image is an instance of NativeImage that stores data of the snapshot. Omitting rect will capture the whole visible page.

contents.hasServiceWorker(callback)

• callback Function

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

contents.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.

contents.print([options])

• options Object (optional)
  • silent Boolean - Don't ask user for print settings. Default is false.
  • printBackground Boolean - Also prints the background color and image of the web page. Default is false.

Prints window's web page. When silent is set to true, 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}).

contents.printToPDF(options, callback)

• options Object
  • marginsType Integer - Specifies the type of margins to use. Uses 0 for default margin, 1 for no margin, and 2 for minimum margin.
  • pageSize String - Specify page size of the generated PDF. Can be A3, A4, A5, Legal, Letter, Tabloid or an Object containing height and width in microns.
  • printBackground Boolean - Whether to print CSS backgrounds.
  • printSelectionOnly Boolean - Whether to print selection only.
  • landscape Boolean - true for landscape, false for portrait.
• callback Function

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

The callback will be called with callback(error, data) on completion. The data is a Buffer that contains the generated PDF data.

By default, an empty options will be regarded as:

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

An example of webContents.printToPDF:

const {BrowserWindow} = require('electron');
const fs = require('fs');

let win = new BrowserWindow({width: 800, height: 600});
win.loadURL('http://github.com');

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

contents.addWorkSpace(path)

• path String

Adds the specified path to DevTools workspace. Must be used after DevTools creation:

win.webContents.on('devtools-opened', () => {
  win.webContents.addWorkSpace(__dirname);
});

contents.removeWorkSpace(path)

• path String

Removes the specified path from DevTools workspace.

contents.openDevTools([options])

• options Object (optional)
  • mode String - Opens the devtools with specified dock state, can be right, bottom, undocked, detach. Defaults to last used dock state. In undocked mode it's possible to dock back. In detach mode it's not.

Opens the devtools.

contents.closeDevTools()

Closes the devtools.

contents.isDevToolsOpened()

Returns whether the devtools is opened.

contents.isDevToolsFocused()

Returns whether the devtools view is focused .

contents.toggleDevTools()

Toggles the developer tools.

contents.inspectElement(x, y)

• x Integer
• y Integer

Starts inspecting element at position (x, y).

contents.inspectServiceWorker()

Opens the developer tools for the service worker context.

contents.send(channel[, arg1][, arg2][, ...])

• channel String
• arg (optional)

Send an asynchronous message to renderer process via channel, you can also send arbitrary arguments. Arguments will be serialized in JSON internally and hence no functions or prototype chain will be included.

The renderer process can handle the message by listening to channel with the ipcRenderer module.

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

// In the main process.
let win = null;

app.on('ready', () => {
  win = new BrowserWindow({width: 800, height: 600});
  win.loadURL(`file://${__dirname}/index.html`);
  win.webContents.on('did-finish-load', () => {
    win.webContents.send('ping', 'whoooooooh!');
  });
});

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

contents.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.

contents.disableDeviceEmulation()

Disable device emulation enabled by webContents.enableDeviceEmulation.

contents.sendInputEvent(event)

• event Object
  • type String (required) - The type of the event, can be mouseDown, mouseUp, mouseEnter, mouseLeave, contextMenu, mouseWheel, mouseMove, 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) - The character that will be sent as the keyboard event. Should only use the valid key codes in Accelerator.

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

contents.beginFrameSubscription([onlyDirty ,]callback)

• onlyDirty Boolean (optional) - Defaults to false
• callback Function

Begin subscribing for presentation events and captured frames, the callback will be called with callback(frameBuffer, dirtyRect) 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).

The dirtyRect is an object with x, y, width, height properties that describes which part of the page was repainted. If onlyDirty is set to true, frameBuffer will only contain the repainted area. onlyDirty defaults to false.

contents.endFrameSubscription()

End subscribing for frame presentation events.

contents.startDrag(item)

• item object
  • file String
  • icon NativeImage

Sets the item as dragging item for current drag-drop operation, file is the absolute path of the file to be dragged, and icon is the image showing under the cursor when dragging.

contents.savePage(fullPath, saveType, callback)

• fullPath String - The full file path.
• saveType String - Specify the save type.
  • HTMLOnly - Save only the HTML of the page.
  • HTMLComplete - Save complete-html page.
  • MHTML - Save complete-html page as MHTML.
• callback Function - (error) => {}.
  • error Error

Returns true if the process of saving page has been initiated successfully.

win.loadURL('https://github.com');

win.webContents.on('did-finish-load', () => {
  win.webContents.savePage('/tmp/test.html', 'HTMLComplete', (error) => {
    if (!error)
      console.log('Save page successfully');
  });
});

contents.showDefinitionForSelection() macOS

Shows pop-up dictionary that searches the selected word on the page.

Instance Properties

contents.id

The unique ID of this WebContents.

contents.session

Returns the session object used by this webContents.

contents.hostWebContents

Returns the WebContents that might own this WebContents.

contents.devToolsWebContents

Get the WebContents of DevTools for this WebContents.

Note: Users should never store this object because it may become null when the DevTools has been closed.

contents.debugger

Get the debugger instance for this webContents.

Class: Debugger

Debugger API serves as an alternate transport for remote debugging protocol.

try {
  win.webContents.debugger.attach('1.1');
} catch(err) {
  console.log('Debugger attach failed : ', err);
};

win.webContents.debugger.on('detach', (event, reason) => {
  console.log('Debugger detached due to : ', reason);
});

win.webContents.debugger.on('message', (event, method, params) => {
  if (method === 'Network.requestWillBeSent') {
    if (params.request.url === 'https://www.github.com')
      win.webContents.debugger.detach();
  }
});

win.webContents.debugger.sendCommand('Network.enable');

Instance Methods

debugger.attach([protocolVersion])

• protocolVersion String (optional) - Requested debugging protocol version.

Attaches the debugger to the webContents.

debugger.isAttached()

Returns a boolean indicating whether a debugger is attached to the webContents.

debugger.detach()

Detaches the debugger from the webContents.

debugger.sendCommand(method[, commandParams, callback])

• method String - Method name, should be one of the methods defined by the remote debugging protocol.
• commandParams Object (optional) - JSON object with request parameters.
• callback Function (optional) - Response
  • error Object - Error message indicating the failure of the command.
  • result Object - Response defined by the 'returns' attribute of the command description in the remote debugging protocol.

Send given command to the debugging target.

Instance Events

Event: 'detach'

• event Event
• reason String - Reason for detaching debugger.

Emitted when debugging session is terminated. This happens either when webContents is closed or devtools is invoked for the attached webContents.

Event: 'message'

• event Event
• method String - Method name.
• params Object - Event parameters defined by the 'parameters' attribute in the remote debugging protocol.

Emitted whenever debugging target issues instrumentation event.