Evaluate JavaScript and resize Browsers (v6.1)

June 25, 2019, 10:19 p.m.

One week after Botfather 6 Beta released we added even more functionality. Scripts can now evaluate Javascript in Browsers and use the returned value. And Browsers can be resized dynamically.

Evaluate Javascript in a Browser (Experimental)

A new method has been added to the Browser type. Scripts can now evalute arbitrary Javascript code in a Browser an use the returned value.

var browser = new Browser("A Test Browser");


var title = browser.evaluateJavascript("document.title;");

Everything except functions can be returned and used, even objects:

var browser = new Browser("Another test Browser");


var location = browser.evaluateJavascript("document.location;");

The Javascript is evaluated in the browsers webhelper process. In case something goes wrong the .evaluateJavascript method has an optional timeout_in_ms parameter. Its default value is 10000 milliseconds.

var browser = new Browser("Timeout Test");

try {
    // Wait 5 seconds for the code to finish executing
    browser.evaluateJavascript("while(true);", 5 * 1000);
} catch (e) {

Beware: This is an experimental feature. At the point of writing evaluating document; still crashes a browsers webhelper process.

Resize browser dynamically

Browsers can now be resized using a new .resize(new Size(...)); method. Furthermore, when creating a new browser, the initial size parameter became optional. A browsers default size is 1366x768.

var browser = new Browser("test");
browser.resize(new Size(900, 600));

Beta available on flathub

If you are a Linux user and want to run Botfather 6.1, type the following command in your commandline:

flatpak remote-add flathub-beta https://flathub.org/beta-repo/flathub-beta.flatpakrepo

flatpak install flathub-beta io.botfather.Botfather

flatpak run io.botfather.Botfather//beta