.. index:: webpage ======= webpage ======= This module provide a ``create()`` function that returns a webpage object. This object allows to load and manipulate a web page. .. code-block:: javascript var page = require("webpage").create(); In the ``page`` variable, you have then an object with many properties and methods. See below. Note: almost properties and methods are implemented, but some are not documented yet. Please help us to document them ;-). You can also read the PhantomJS documentation. Index of properties and methods -------------------------------- Navigation: :ref:`canGoBack `, :ref:`canGoForward `, :ref:`navigationLocked ` :ref:`go() ` , :ref:`goBack() `, :ref:`goForward() ` :ref:`onNavigationRequested ` Frames and windows management: :ref:`focusedFrameName `, :ref:`frameContent `, :ref:`frameName `, :ref:`framePlainText `, :ref:`frameTitle `, :ref:`frameUrl `, :ref:`framesCount `, :ref:`framesName `, :ref:`ownsPages `, :ref:`pages `, :ref:`pagesWindowName `, :ref:`url `, :ref:`windowName ` :ref:`childFramesCount() `, :ref:`childFramesName() `, :ref:`close() `, :ref:`currentFrameName() `, :ref:`getPage() `, :ref:`open() `, :ref:`openUrl() `, :ref:`release() `, :ref:`reload() `, :ref:`stop() `, :ref:`switchToFocusedFrame() `, :ref:`switchToFrame() `, :ref:`switchToChildFrame() `, :ref:`switchToMainFrame() `, :ref:`switchToParentFrame() ` :ref:`onPageCreated `, :ref:`onClosing `, :ref:`onUrlChanged ` Offline storage: :ref:`offlineStoragePath `, :ref:`offlineStorageQuota ` Rendering: :ref:`clipRect `, :ref:`paperSize `, :ref:`viewportSize `, :ref:`zoomFactor ` :ref:`render() `, :ref:`renderBase64() ` :ref:`renderBytes() ` Content management: :ref:`captureContent `, :ref:`content `, :ref:`plainText `, :ref:`scrollPosition `, :ref:`title ` :ref:`setContent() `, :ref:`uploadFile() ` :ref:`onAlert `, :ref:`onAuthPrompt `, :ref:`onCallback `, :ref:`onConfirm `, :ref:`onConsoleMessage `, :ref:`onFilePicker `, :ref:`onPrompt ` Javascript execution: :ref:`evaluateJavaScript() `, :ref:`evaluate() `, :ref:`evaluateAsync() `, :ref:`includeJs() `, :ref:`injectJs() `, :ref:`stopJavaScript() ` :ref:`onLongRunningScript `, :ref:`onError ` Cookies management: :ref:`cookies `, :ref:`addCookie() ` :ref:`clearCookies() `, :ref:`deleteCookie() ` Network management: :ref:`customHeaders ` :ref:`onInitialized `, :ref:`onLoadFinished `, :ref:`onLoadStarted ` :ref:`onResourceError `, :ref:`onResourceRequested `, :ref:`onResourceReceived `, :ref:`onResourceTimeout ` Page events: :ref:`event `, :ref:`sendEvent() ` Others properties: :ref:`libraryPath ` :ref:`settings ` Internal methods to trigger callbacks: :ref:`closing() `, :ref:`initialized() `, :ref:`javaScriptAlertSent() `, :ref:`javaScriptConsoleMessageSent() `, :ref:`loadFinished() `, :ref:`loadStarted() `, :ref:`navigationRequested() `, :ref:`rawPageCreated() `, :ref:`resourceError() `, :ref:`resourceReceived() `, :ref:`resourceRequested() `, :ref:`urlChanged() ` Properties =========== .. _webpage-clipRect: clipRect ----------------------------------------- This is an object indicating the coordinates of an area to capture, used by the ``render()`` method. It contains four properties: ``top``, ``left``, ``width``, ``height``. To modify it, set an entire object on this property. .. code-block:: javascript page.clipRect = { top: 14, left: 3, width: 400, height: 300 }; .. _webpage-canGoBack: canGoBack ----------------------------------------- Indicates if there is a previous page in the navigation history. This is a boolean. Read-only. .. _webpage-canGoForward: canGoForward ----------------------------------------- Indicates if there is a next page in the navigation history. This is a boolean. Read-only. .. _webpage-captureContent: captureContent ----------------------------------------- This is an array of regexp matching content types of resources for which you want to retrieve the content. The content is then set on the body property of the response object received by your :ref:`onResourceReceived callback `. .. code-block:: javascript webpage.captureContent = [ /css/, /image\/.*/ ] This limitation exists to avoid to take memory uselessly (in the case where you don't need the ``body`` property), since resources like images or videos could take many memory. (SlimerJS only) .. _webpage-content: content ----------------------------------------- This property contain the source code of the actual webpage. You can set this property with the source code of an HTML page to replace the content of the current web page. .. _webpage-cookies: cookies ----------------------------------------- This is an array of all :doc:`Cookie objects ` stored in the current profile, and which corresponds to the current url of the webpage. When you set an array of Cookie to this property, cookies will be set for the current url: their domain and path properties will be changed. Note: modifying an object in the array won't modify the cookie. You should retrieve the array, modify it, and then set the ``cookies`` property with this array. Probably you would prefer to use the ``addCookie()`` method to modify a cookie. If cookies are disabled, or if no page is loaded, modifying this property does nothing. Be careful about `the inconsistent behavior of the expiry property `_. .. _webpage-customHeaders: customHeaders ----------------------------------------- .. index:: customHeaders This property is an object defining additional HTTP headers that will be send with each HTTP request, both for pages and resources. Example: .. code-block:: javascript webpage.customHeaders = { "foo": "bar" } To define user agent, prefer to use ``webpage.settings.userAgent`` .. container:: warning **Warning**: Do not set headers that contain sensitive information, like authentication username/password, cookies etc! It can be a security issue! Remember that all custom headers are sent with **every requests** made during the load of the web page. And as you may know, a web page can load ressources from everywhere. If you set http authentication username/password into headers, and if the web page loaded from the web site A, contains an iframe that loads a page from another web site B, this website will receive all custom headers, and then **the username and password**, although it should not! - To set cookies, prefer to use the :ref:`cookies property `. - To set http authentication username and password, prefer to use :ref:`settings ` or better, define an ``onAuthPrompt`` callback (version 0.9+) with which you can precisely indicate credentials for specific hosts. - If you want to set headers only for the main request of the web page, use the ``httpConf`` parameter to the :ref:`open() method ` or the :ref:`openUrl() method `. .. _webpage-event: event ----------------------------------------- This is an object (read only) that hosts some constants to use with ``sendEvent()``. There is a ``modifier`` property containing constants for key modifiers: .. code-block:: javascript page.event.modifier.shift page.event.modifier.ctrl page.event.modifier.alt page.event.modifier.meta page.event.modifier.keypad There is also a ``key`` property containing constants for key codes. .. _webpage-focusedFrameName: focusedFrameName ----------------------------------------- Contains the name of the child frame that has the focus. Read only. .. _webpage-frameContent: frameContent ----------------------------------------- This property contain the source code of `the selected frame <../manual/frames-manipulation.html>`_. You can set this property with the source code of an HTML page to replace the content of the current frame. .. _webpage-frameName: frameName ----------------------------------------- Contains the name of `the selected frame <../manual/frames-manipulation.html>`_. Read only. .. _webpage-framePlainText: framePlainText ----------------------------------------- Contains the text version of the content of `the selected frame <../manual/frames-manipulation.html>`_. Read only. .. _webpage-frameTitle: frameTitle ----------------------------------------- Contains the title of `the selected frame <../manual/frames-manipulation.html>`_. Read only. .. _webpage-frameUrl: frameUrl ----------------------------------------- Contains the URL of `the selected frame <../manual/frames-manipulation.html>`_. Read only. .. _webpage-framesCount: framesCount ----------------------------------------- Contains the number of child frames of `the selected frame <../manual/frames-manipulation.html>`_. Read only. .. _webpage-framesName: framesName ----------------------------------------- Contains the list of names of child frames of `the selected frame <../manual/frames-manipulation.html>`_. Read only. .. _webpage-libraryPath: libraryPath ----------------------------------------- Implemented. Documentation needed. .. _webpage-navigationLocked: navigationLocked ----------------------------------------- This is a property to lock navigation. If it is ``true``, clicking on a link in the web page to load a new page, submitting a form etc, will not have effect. .. _webpage-offlineStoragePath: offlineStoragePath ----------------------------------------- Indicates the path of the sqlite file where content of window.localStorage is stored. Read only. Note: in PhantomJS, this is the path of a directory. The storage is different than in Gecko. Contrary to PhantomJS, this property cannot be changed with the ``--local-storage-path`` flag from the command line. .. _webpage-offlineStorageQuota: offlineStorageQuota ----------------------------------------- Contains the maximum size of data for a page, stored in window.localStorage. The number is in Bytes. Default is 5 242 880 (5MB). Read only. To change this number, use the ``--local-storage-quota`` flag in the command line. .. _webpage-ownsPages: ownsPages ----------------------------------------- This boolean indicates if pages opening by the webpage (by `window.open()`) should be children of the webpage (true) or not (false). Default is true. When it is true, child pages appears in the `pages` property. .. _webpage-pages: pages ----------------------------------------- This is the list of child pages that the page has currently opened with `window.open()`. If a child page is closed (by `window.close()` or by `webpage.close()`), the page is automatically removed from this list. You should not keep a strong reference to this array since you obtain only a copy, so in this case you won't see changes. If "ownsPages" is "false", this list won't owns the child pages. .. _webpage-pagesWindowName: pagesWindowName ----------------------------------------- list of window name (strings) of child pages. The window name is the name given to `window.open()`. The list is only from child pages that have been created when ownsPages was true. .. _webpage-paperSize: paperSize ----------------------------------------- Contains an object specifiying some dimensions for the PDF rendering. If null, the PDF size will be the viewport size of the webpage. It can be either: .. code-block:: javascript {width:'', height:'', margin:''} or .. code-block:: javascript {format:'', orientation:'', margin:''} Margin (optional) can be a single dimension or an object containing one or more of the following properties: 'top', 'left', 'bottom', 'right'. Default is 0. Dimensions in width, height, margin should be a number following by a unit: 'mm', 'cm', 'in', 'px'. No unit means 'px'. Format should one of these strings : "A4", "B5", "Letter", "Legal", "Executive", "A0", "A1", "A2", "A3", "A5", "A6", "A7", "A8", "A9", "B0", "B1", "B10", "B2", "B3", "B4", "B6", "B7", "B8", "B9", "C5E", "Comm10E", "DLE", "Folio", "Ledger", "Tabloid". Orientation (optional) is "landscape" or 'portrait' (default). 'header' and 'footer' properties supported in PhantomJS are not supported yet by SlimerJS. SlimerJS supports 'headerStr' and 'footerStr' properties which are static text with following special symbols interpretation. ==================== =========================================================== Variable Description ==================== =========================================================== ``&T`` title ``&U`` URL ``&D`` date/time ``&P`` current page number ``&PT`` total number of pages in form "*page* ``of`` *total*" ``&L`` last page number ==================== =========================================================== The font of header and footer can't be modified. 'headerStr' and 'footerStr' can be objects with properties for position (left,center,right) of header/footer. .. code-block:: javascript { headerStr:{left:'', center:'&T', right:''} , footerStr:{left:'', center:'', right:'&P of &L'} } SlimerJS supports following additional properties of paperSize. - ``unwriteableMargin``: unwriteable margins - ``edge`` : positioning of the headers and footers on the page. They're measured as an offset from the unwriteable margin - ``shrinkToFit``: try to fit content in page (bool) - ``printBGColors``, ``printBGImages``: control printing of background colors and images (bool) - ``title``: title of printed content (see 'headerStr' and 'footerStr') .. _webpage-plainText: plainText ----------------------------------------- Contains the content of the web page as text. For html pages, you'll have only texts of the page. Read only. .. _webpage-scrollPosition: scrollPosition ----------------------------------------- This property contains an object indicating the scrolling position. You can read or modify it. The object contains two properties: ``top`` and ``left`` Example: .. code-block:: javascript page.scrollPosition = { top: 100, left: 0 }; .. _webpage-settings: settings ----------------------------------------- .. index:: settings This property allows to set some options for the load of a page. Changing them after the load has no effect. - ``javascriptEnabled``: ``false`` to deactivate javascript in web pages (default is ``true``) - ``javascriptCanCloseWindows`` (not supported yet) - ``javascriptCanOpenWindows`` (not supported yet) - ``loadImages``: ``false`` to deactivate the loading of images (default is ``true``) - ``localToRemoteUrlAccessEnabled`` (not supported yet) - ``maxAuthAttempts``: indicate the maximum of attempts of HTTP authentication. (SlimerJS 0.9) - ``password``: password to give to HTTP authentication (SlimerJS 0.9) - ``userAgent``: string to define the user Agent in HTTP requests. By default, it is something like ``"Mozilla/5.0 (X11; Linux x86_64; rv:21.0) Gecko/20100101 SlimerJS/0.7"`` (depending of the version of Firefox you use), or the value set by the ``--user-agent`` command line option. - ``userName``: username to give to HTTP authentication (SlimerJS 0.9) - ``XSSAuditingEnabled`` (not supported yet) - ``webSecurityEnabled`` (not supported yet) - ``plainTextAllContent``: ``true`` to indicate that webpage.plainText returns everything, even content of ``script`` elements, invisible elements etc.. Default: ``false``. (SlimerJS only) - ``resourceTimeout``: the number of milliseconds that the browser should wait after the loading of a resource. ``undefined`` (default value) means default gecko parameters. .. code-block:: javascript page.settings.userAgent = "My Super Agent / 1.0" .. container:: warning user name and password indicated into settings are given to the server of the main loaded webpage (if it asks them), but also to all servers that are called for some resources and that ask an http authentication! Without knowing it, you can give these sensitive information to a web resource loading from an other domain than the main page and which asks http authentication (like an iframe, a css stylesheets etc..). If you want a better control of the authentication, use the ``httpConf`` parameter on the :ref:`open() ` or :ref:`openUrl() ` method, or use the callback :ref:`onAuthPrompt `. .. _webpage-title: title ----------------------------------------- It allows to retrieve the title of the loaded page. (Readonly) .. _webpage-url: url ----------------------------------------- This property contains the current url of the page. If nothing is loaded yet, this is an empty string. Read only. .. _webpage-viewportSize: viewportSize ----------------------------------------- This property allows to change the size of the viewport, e.g., the size of the window where the webpage is displayed. (default is ``{width: 400, height: 300}`` or the values from the ``--viewport-width`` and ``--viewport-height`` command line options.) It is useful to test the display of the web page in different size of windows. ``viewportSize`` is an object with with ``width`` and ``height`` properties, containing the size in pixels. Note that changing this property triggers a reflow of the rendering and this is done asynchronously (this is how browser rendering engines work). So for example, if you take a screenshot with ``webpage.render()`` just after setting the viewportSize, you may not have the final result (you call ``render()`` too early). .. code-block:: javascript page.viewportSize = { width: 480, height: 800 }; .. _webpage-windowName: windowName ----------------------------------------- Contains the name of the window, e.g. the name given to ``window.open()`` if the page has been opened with this method. .. _webpage-zoomFactor: zoomFactor ----------------------------------------- Contains the zoom factor of the webpage display. Setting a value to this property decreases or increases the size of the web page rendering. A value between 0 and 1 decreases the size of the page, and a value higher than 1 increases its size. ``1`` means no zoom (normal size). Note that changing its value refreshes the display of the page asynchronously. So for example, if you call :ref:`render() ` just after setting a value on ``zoomFactor``, the screenshot may not represent the final result (``render()`` is called too early). After the call of ``zoomFactor``, You probably have to put the code into a callback given to ``window.setTimeout()``, or you can call ``slimer.wait(500)`` (which is not compatible with PhantomJS). Methods ======== .. _webpage-addCookie: addCookie(cookie) ----------------------------------------- Add a cookie in the cookies storage of the current profile, for the current url. The parameter is :doc:`a Cookie object `. The domain and the path of the cookie will be set to the domain and the path of the current url. It returns true if the cookie has been really added. If cookies are disabled, or if no page is loaded, the cookie is not added into the cookie database. Be careful about `the inconsistent behavior of the expiry property `_. .. _webpage-childFramesCount: childFramesCount() ----------------------------------------- Returns the number child frames of `the selected frame <../manual/frames-manipulation.html>`_. Deprecated. Use :ref:`framesCount ` instead. .. _webpage-childFramesName: childFramesName() ----------------------------------------- Returns the list of the names of child frames of `the selected frame <../manual/frames-manipulation.html>`_. Deprecated. Use :ref:`framesName ` instead. .. _webpage-clearCookies: clearCookies() ----------------------------------------- Delete all cookies corresponding to the current url. .. _webpage-close: close() ----------------------------------------- Close the web page. It means that it closes the window displaying the web page. After the close, some methods cannot be used and you should call ``open()`` or ``openUrl()`` to be able to reuse the webpage object. .. _webpage-currentFrameName: currentFrameName() ----------------------------------------- Returns the name of `the selected frame <../manual/frames-manipulation.html>`_. Deprecated. Use :ref:`frameName ` instead. .. _webpage-deleteCookie: deleteCookie(cookiename) ----------------------------------------- It deletes all cookies that have the given name and corresponding to the current url. It returns true if some cookies have been deleted. It works only if cookies are enabled. .. _webpage-evaluateJavaScript: evaluateJavaScript(src) ----------------------------------------- Evaluate the current javascript source (in a string), into the context of the loaded web page, or if a frame is selected, into the context of `the selected frame <../manual/frames-manipulation.html>`_. It returns the result of the evaluation. .. _webpage-evaluate: evaluate(func, arg1, arg2...) ----------------------------------------- It executes the given function in the context of the loaded web page, or if a frame is selected, into the context of `the selected frame <../manual/frames-manipulation.html>`_. It means that the code of the function cannot access to objects and variables of your script. For example, in this function, the ``document`` and ``window`` objects are belongs to the loaded page, not to your script. In other terms, you cannot use closures. .. code-block:: javascript var page = require('webpage').create(); page.open("http://example.com", function (status) { var someContent = page.evaluate(function () { return document.querySelector("#aDiv").textContent; }); console.log('The introduction: ' + someContent); slimer.exit() }); You can give additional parameters to ``evaluate()``. This will be the parameters for the function. For example, here the function will receive "#aDiv" as parameter: .. code-block:: javascript var someContent = page.evaluate(function (selector) { return document.querySelector(selector).textContent; }, "#aDiv"); Parameters can only some basic javascript objects or literal values. You cannot pass some objects like DOM elements. In other terms, you cannot pass parameters on which you cannot call a ``toString()`` or you cannot serialize as a JSON value. ``evaluate()`` returns the value returned by the function. .. _webpage-evaluateAsync: evaluateAsync(func, timeMs, arg1, arg2...) ------------------------------------------- It is equivalent to ``evaluate()``, but with some differences: - the function is executed asynchronously. It means that the call of ``evaluateAsync()`` does not wait after the execution of the given function to return. It does not block your current script. The script can be executed after the given number of milliseconds (timeMs). - you cannot return values inside the given function .. _webpage-getPage: getPage(windowName) ----------------------------------------- This methods returns the child page that matches the given "window.name". Only children opened when ownsPage was true are checked. .. _webpage-go: go(indexIncrement) ----------------------------------------- This method allows to navigate into the navigation history. The parameter, an integer, indicates how far to move forward or backward in the navigation history. .. code-block:: javascript webpage.go(-3); webpage.go(-1); // equivalent to webpage.goBack() webpage.go(1); // equivalent to webpage.goForward() webpage.go(4); .. _webpage-goBack: goBack() ----------------------------------------- Displays the previous page in the navigation history. .. _webpage-goForward: goForward() ----------------------------------------- Displays the next page in the navigation history. .. _webpage-includeJs: includeJs(url, callback) ----------------------------------------- It loads into the current web page, the javascript file stored at the given url. If `a frame is selected <../manual/frames-manipulation.html>`_, the file is loaded into this frame. When the load is done, the given callback is called. .. _webpage-injectJs: injectJs(filename) ----------------------------------------- It loads and executes the given javascript file into the context of the current web page. If `a frame is selected <../manual/frames-manipulation.html>`_, the file is executed into this frame. If the given filename is a relative path, SlimerJS tries to resolve the full path from the current working directory (that is the directory from which SlimerJS has been launched). If the file is not found, SlimerJS tries to resolve with the libraryPath. Note: there is a limitation in SlimerJS. If the loaded script wants to modify a variable of the current web page/frame, it should call ``window.myvariable = '..'`` instead of ``myvariable = '..'``. .. _webpage-stopJavaScript: stopJavaScript() ----------------------------------------- Stop long running JavaScript within `onLongRunningScript` callback. Called outside of the `onLongRunningScript` callback it does nothing. .. _webpage-open: open(url...) ----------------------------------------- .. index:: open, promise .. _promise: https://addons.mozilla.org/en-US/developers/docs/sdk/latest/modules/sdk/core/promise.html This method allows to open a page into a virtual browser. Since this operation is asynchronous, you cannot do something on the page after the call of ``open()``. You should provide a callback or you should use the returned promise_ (not compatible with PhantomJS), to do something on the loaded page. The callback or the promise receives a string "success" if the loading has been succeded. Example with a callback function: .. code-block:: javascript page.open("http://slimerjs.org", function(status){ if (status == "success") { console.log("The title of the page is: "+ page.title); } else { console.log("Sorry, the page is not loaded"); } }) Example with the returned promise_ (not compatible with PhantomJS): .. code-block:: javascript page.open("http://slimerjs.org") .then(function(status){ if (status == "success") { console.log("The title of the page is: "+ page.title); } else { console.log("Sorry, the page is not loaded"); } }) To load two pages, one after an other, here is how to do: .. code-block:: javascript page.open("http://example.com/page1", function(status){ // do something on the page... page.open("http://example.com/page2", function(status){ // do something on the page... }) }) With the promise_, it's better in term of code (not compatible with PhantomJS): .. code-block:: javascript page.open("http://example.com/page1") .then(function(status){ // do something on the page... return page.open("http://example.com/page2") }) .then(function(status){ // do something on the page... // etc... return page.open("http://example.com/page3") }) To load N pages in parallel, here is how to do: .. code-block:: javascript const URLS = [ 'http://example.com/page1', 'http://example.com/page2' ]; var queue = []; URLS.forEach(function(url) { var p = new Promise(function(resolve, reject) { var page = require('webpage').create(); page.open(url) .then(function(status) { if (status == "success") { var title = page.title; console.log("Page title of " + url + " : " + title); page.close(); resolve([url, title]); } else { console.log("Sorry, the page is not loaded for " + url); reject(new Error("Some problem occurred with " + url)); } }); }); queue.push(p); }); Promise.all(queue).then(function(values) { console.log(values); phantom.exit(); }); **Other arguments:** The ``open()`` method accepts several arguments: - ``open(url)`` - ``open(url, callback)`` - ``open(url, httpConf)`` - ``open(url, httpConf, callback)`` - ``open(url, operation, data)`` - ``open(url, operation, data, callback)`` - ``open(url, operation, data, headers, callback)`` Remember that in all cases, the method returns a promise_. ``httpConf`` is an object. See :ref:`webpage.openUrl ` below. ``operation``, ``data`` and ``headers`` should have same type of values as you can find in ``httpConf``. Note that ``open()`` call in fact ``openUrl()``. .. _webpage-openUrl: openUrl(url, httpConf, settings, callback) ------------------------------------------- .. index:: openUrl, promise Like ``open()``, it loads a webpage. The only difference is the number and the type of arguments. ``httpConf`` is an object with these properties: - ``httpConf.operation``: the http method. Allowed values: ``'get'`` or ``'post'`` (other methods are not supported in SlimerJS) - ``httpConf.data``: the body. Useful only for ``'post'`` method - ``httpConf.headers``: the headers to send. An object like :ref:`webpage.customHeaders `, but it doesn't replace ``webpage.customHeaders``. It allows you to specify additional headers for this specific load. ``httpConf`` is optional and you can give ``null`` instead of an object. The default method will be ``'get'``, without data and without specific headers.s ``settings`` is an object like :ref:`webpage.settings `. In fact the given value changes ``webpage.settings``. You can indicate ``null`` if you don't want to set new settings. ``callback`` is a callback function, called when the page is loaded. ``openUrl()`` returns a promise. .. _webpage-release: release() ----------------------------------------- Similar to :ref:`close() `. This method is deprecated in PhantomJS. ``webpage.close()`` should be used instead. .. _webpage-reload: reload() ----------------------------------------- Reload the current web page. .. _webpage-render: render(filename, options) ----------------------------------------- This method takes a screenshot of the web page and stores it into the given file. You can limit the area to capture by setting the ``clipRect`` property. By default, it determines the format of the file by inspecting its extension. It supports only JPG, PNG and PDF format (and gif probably in future version). The second parameter is an object containing options. Here are its possible properties: - ``format``: indicate the file format (then the file extension is ignored). possible values: ``jpg``, ``png``, ``jpeg``, ``pdf``, ``bmp`` and ``ico``. Gecko doesn't have a GIF encoder so it is not available. - ``quality``: the compression quality. A number between 0 and 100 (in SlimerJS 0.9.2 and lower, it was between 0 and 1) - ``ratio``: (SlimerJS only), a number between 0 and 1, indicating the "zoom level" of the capture. (``zoomFactor`` is then ignored). - ``onlyViewport``: (SlimerJS only), set to true if you only want to take a screenshot of the current viewport. By default, it is false, and screenshot has the size of the content, except when webpage.clipRect is set. Note: because of a limitation of Gecko (see `Mozilla bug 650418 `_), plugins content like flash cannot be rendered in the screenshot (even if you can see it in the window). Except in the case where the ``