I would like to inject an external javascript code into a certain webpage in a mobile phone browser such as chrome or opera mini. On computers, we can do this directly in the console or through extensions such as Scripty. Unfortunately, phone browsers don't show consoles nor do they have extensions. Please how can I achieve this?
You can use eruda. It's a console for mobile browsers. It also has many plugins such as eruda-touches which visualizes all current touches and their positions. Personally, I made a bookmark using chrome browser on my phone to implement this console directly in any page when i search for its name. Watch this youtube video for more details.