Singleton that connects the engine with the browser's JavaScript context in HTML5 export.
The JavaScript singleton is implemented only in HTML5 export. It's used to access the browser's JavaScript context. This allows interaction with embedding pages or calling third-party JavaScript APIs.
https://docs.godotengine.org/en/latest/getting_started/workflow/export/exporting_for_web.html#calling-javascript-from-script
Execute the string [code]code[/code] as JavaScript code within the browser window. This is a call to the actual global JavaScript function [code]eval()[/code]. If [code]use_global_execution_context[/code] is [code]true[/code], the code will be evaluated in the global execution context. Otherwise, it is evaluated in the execution context of a function within the engine's runtime environment.