# Evaluate Js
Run Javascript code from Python.
import webview
from webview.errors import JavascriptException
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)
try:
result = window.evaluate_js('syntaxerror#$%#$')
except JavascriptException as e:
print('Javascript exception occured: ', e)
if __name__ == '__main__':
window = webview.create_window('Run custom JavaScript', html='<html><body></body></html>')
webview.start(evaluate_js, window)