[Web] Expand "Interacting with Javascript"

[Faless]

Document the new (preferred) interface.

Add a small section about downloading files to the user device.

Based on: https://godotengine.org/article/godot-web-progress-report-9/

Should be back-ported to 3.x/3.5 for which it needs changes to the code block about to_utf8_buffer/to_utf8, create_callback argument types, and FileAccess/File .

[Faless]

@TheYellowArchitect thanks for the review! Fixed :)

[Faless]

@AThousandShips thanks! Fixed :)

[mhilbrunner]

Some suggestions below. In general, this tutorial uses a lot of code comments for explanations, which is problematic as they (currently) can't be translated, which admittedly is a fault of our tooling. Where possible, it would be good to move more explanations to the tutorial text.

Otherwise, this looks good to me and covers something frequently asked about :)

[Faless]

Some suggestions below. In general, this tutorial uses a lot of code comments for explanations, which is problematic as they (currently) can't be translated, which admittedly is a fault of our tooling. Where possible, it would be good to move more explanations to the tutorial text.

I've applied the suggestions.

As discussed in chat, I'd rather merge this and stop telling people to use eval (which is terrible) 3 years after this feature was merged.

Hopefully we can find someone to improve this in follow up PRs, since I won't have time to work more on this (I also have to port the Multiplayer Replication article).

EDIT: Also, thanks for the in-depth review! :)

[mhilbrunner]

Thank you! :) Merged.

[mhilbrunner]

Cherry-picked to 4.2 in #9647.