Access local javascript variable

[tct123]

Question

@ndonkoHenri how can i access javascript variables in flet? i only need it for webdevelopmet.

Code sample

No response

Error message

No response

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• I have searched for answers to my question both in the issues and in previous discussions.

[Pecinallix]

Using page.run_javascript()
Flet provides the page.run_javascript() method, which allows you to execute arbitrary JavaScript code from Python. This is useful for interacting with JavaScript variables or performing DOM manipulations.

Example:

import flet as ft

def main(page: ft.Page):
# Execute JavaScript to access a variable
js_variable = "window.myVariable"
result = page.run_javascript(f"typeof {js_variable} !== 'undefined' ? {js_variable} : null")

# Print the result (this will be available in the browser console)
print("JavaScript variable value:", result)

# Update the page with the result
page.add(ft.Text(f"Value of JavaScript variable: {result}"))

ft.app(target=main, view=ft.WEB_BROWSER)

[Klu1d]

What does page.run_javascript mean? I don't quite understand this line. Does page have such a method, or is it created at this moment?

[Pecinallix]

Yes, page.run_javascript() is a built-in method provided by Flet specifically for executing JavaScript code in the browser environment. This method allows you to run arbitrary JavaScript code directly from your Python code.

Purpose : It enables communication between Python (your Flet app logic) and JavaScript (the browser environment).
Usage : You pass a string containing valid JavaScript code to this method, and Flet executes it in the browser.
Return Value : The result of the JavaScript execution can be captured and used in your Python code.

[Klu1d]

Hi again,
Since reading your message, I hadn’t tried testing what you mentioned.

But now I suddenly wanted to give it a try — and I didn’t get any result.
Are you sure about what you said? Maybe you could show a working example?

import flet as ft

def main(page: ft.Page):
    js_variable = "window.myVariable"
    result = page.run_javascript(f"typeof {js_variable} !== 'undefined' ? {js_variable} : null")

    print("JavaScript variable value:", result)
    page.add(ft.Text(f"Value of JavaScript variable: {result}"))

ft.app(target=main, view=ft.WEB_BROWSER)

@ndonkoHenri Could you also comment on this?

[prosanyasi]

Are you using the Flet Webview to display a local HTML page because the run_javascript is a method of the WebView.