flutter Webview file choser and javascript injection

[katlego namate]

Good day is there a way to inject javascript into the webview before or on page load of the website and also allow upload button in the website be able to open file chooser in android or ios?

Please help time is not on my side i really need to deliver this web app fast with custom javascript edits (by DOM) on page load and make the webview able to open the file chooser