Selenium Webdriver: execute_script can't execute custom methods and external javascript files

Question

I'm working with Selenium and Python and I'm trying to do two things:

Import an external javascript file and execute a method defined there
Define methods on a string and call them after evaluating

This is the output for the first case:

test.js

function hello(){
  document.body.innerHTML = "testing";
}

Python code

>>> from selenium import webdriver
>>> f = webdriver.Firefox()
>>> f.execute_script("var s=document.createElement('script');\
...                                s.src='file://C:/test.js';\
...                                s.type = 'text/javascript';\
...                                document.head.appendChild(s)")
>>> f.execute_script("hello")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\site-packages\selenium-2.41.0-py2.7.egg\selenium\webdriver\remote\webdriver.py", line 394, in execute_script
{'script': script, 'args':converted_args})['value']
  File "C:\Python27\lib\site-packages\selenium-2.41.0-py2.7.egg\selenium\webdriver\remote\webdriver.py", line 166, in execute
self.error_handler.check_response(response)
  File "C:\Python27\lib\site-packages\selenium-2.41.0-py2.7.egg\selenium\webdriver\remote\errorhandler.py", line 164, in check_response
raise exception_class(message, screen, stacktrace) selenium.common.exceptions.WebDriverException: Message: u'hello is not defined' ; Stacktrace:
  at anonymous (about:blank:68)
  at handleEvaluateEvent (about:blank:68)

And for the second case:

>>> js = "function blah(){document.body.innerHTML='testing';}"
>>> f.execute_script(js)
>>> f.execute_script("blah")
    ...
    raise exception_class(message, screen, stacktrace) selenium.common.exceptions.WebDriverException: Message: u'blah is not defined' ; Stacktrace:

Louis · Accepted Answer · 2014-04-23 14:56:26Z

10

I can get your first case to work if I create an empty html file and issue:

f = webdriver.Firefox()
f.get("file://path/to/empty.html")

After this, the JavaScript you've shown will execute without issue. When I try the code you've shown in the question, Firefox does not give me an error but Chrome says: "Not allowed to load local resource". I believe the problem is cross-domain requests.

The issue with your second case is that behind the scenes Selenium wraps your JavaScript code in an anonymous function. So your blah function is local to this anonymous function. If you want to make it global, you have to assign it to window, like this:

>>> from selenium import webdriver
>>> f = webdriver.Firefox()
>>> f.execute_script("window.blah = function () {document.body.innerHTML='testing';}")
>>> f.execute_script("blah()")

edited Apr 23, 2014 at 14:56

answered Apr 22, 2014 at 22:48

Louis

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3 Comments

estemendoza Over a year ago

Thanks for your response, I understand the error on the first case, but the second case, it didn't work for me (at least it's not giving me more error but nothing happens) Where you able to make it work? If so, could you please share the code?. Thanks!

estemendoza Over a year ago

Thanks! It worked, I was making the call without the "()" like this f.execute_script("blah")

Learner Over a year ago

Awesome explanation!! superb, cool and worth nothing to mention!! Broadened my horizon.

Green Lithium · Accepted Answer · 2016-09-12 15:33:02Z

1

driver.execute_script("window.a = function(a,b) {return a + b;}")


print driver.execute_script("return a(1,2)")

edited Sep 12, 2016 at 15:33

Green Lithium

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answered Sep 12, 2016 at 9:52

user6729158

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