to set MutationObserver, How to inject javascript before page-loading using Selenium

Question

I'm trying to set MutationObserver for observing page mutation while loading.

In order to do that, MutationObserver should be configured before page loading.

With selenium-chromedriver, couldn't find the way to inject JS for such purpose.

I know chrome extension can do that but extensions won't work on headless mode.

That's the problem.

Answer 1

We can now use execute_cdp_cmd(cmd, cmd_args) to execute Chrome Devtools Protocol command in Selenium

from selenium import webdriver

driver = webdriver.Chrome()

driver.execute_cdp_cmd(
    "Page.addScriptToEvaluateOnNewDocument",
    {
        "source": """// Your JavaScript here"""
    }
)

driver.get("https://stackoverflow.com")
driver.quit()

The argument for "source" is just a string. So you can actually write your script in a .js file (for syntax highlighting) and read it using Python