Javascript evaluation

Evaluate Javascript from Python code.

import webview

def evaluate_js(window):
    result = window.evaluate_js(
        r"""
        var h1 = document.createElement('h1')
        var text = document.createTextNode('Hello pywebview')
        h1.appendChild(text)
        document.body.appendChild(h1)

        document.body.style.backgroundColor = '#212121'
        document.body.style.color = '#f2f2f2'

        // Return user agent
        'User agent:\n' + navigator.userAgent;
        """
    )

    print(result)


if __name__ == '__main__':
    window = webview.create_window('Run custom JavaScript')
    webview.start(evaluate_js, window)