[HTML5] Implement Godot <-> JavaScript interface.

[Faless]

4.0 version of: #48691 .

The API is the same, with the exception of JavaScript.create_callback which now takes a callable (first line below):

var _my_js_callback = JavaScript.create_callback(myCallback) # This reference must be kept
var console = JavaScript.get_interface("console")

func _init():
	var buf = JavaScript.create_object("ArrayBuffer", 10) # new ArrayBuffer(10)
	print(buf) # prints [JavaScriptObject:OBJECT_ID]
	var uint8arr = JavaScript.create_object("Uint8Array", buf) # new Uint8Array(buf)
	uint8arr[1] = 255
	prints(uint8arr[1], uint8arr.byteLength) # prints 255 10
	console.log(uint8arr) # prints in browser console "Uint8Array(10) [ 0, 255, 0, 0, 0, 0, 0, 0, 0, 0 ]"

	# Equivalent of JavaScript: Array.from(uint8arr).forEach(myCallback)
	JavaScript.get_interface("Array").from(uint8arr).forEach(_my_js_callback)

func myCallback(args):
	# Will be called with the parameters passed to the "forEach" callback
	# [0, 0, [JavaScriptObject:1173]]
	# [255, 1, [JavaScriptObject:1173]]
	# ...
	# [0, 9, [JavaScriptObject:1180]]
	print(args)

Not really easy to test in current master, but you can build the thread version:
scons p=javascript target=release_debug threads_enabled=yes
And check the console. If the startup get stuck, try editing platform/javascript/js/libs/library_godot_os.js and have godot_js_os_hw_concurrency_get always return 2 (otherwise Godot will spawn to many threads and crash your browser).

[akien-mga]

That would be more readable as viii ;) (ok I'm pretty sure I already made that joke last year :P)

[akien-mga]

Thanks!