The JavaScript singleton is implemented only in the HTML5 export. It's used to access the browser's JavaScript context. This allows interaction with embedding pages or calling third-party JavaScript APIs.
<linktitle="Exporting for the Web: Calling JavaScript from script">https://docs.godotengine.org/en/latest/getting_started/workflow/export/exporting_for_web.html#calling-javascript-from-script</link>
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.