Singleton that connects the engine with the browser's JavaScript context in HTML5 export. 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. [b]Note:[/b] This singleton can be disabled at build-time to improve security. By default, the JavaScript singleton is enabled. Official export templates also have the JavaScript singleton enabled. See [url=$DOCS_URL/development/compiling/compiling_for_web.html]Compiling for the Web[/url] in the documentation for more information. $DOCS_URL/tutorials/export/exporting_for_web.html#calling-javascript-from-script Creates a reference to a [Callable] that can be used as a callback by JavaScript. The reference must be kept until the callback happens, or it won't be called at all. See [JavaScriptObject] for usage. Creates a new JavaScript object using the [code]new[/code] constructor. The [code]object[/code] must a valid property of the JavaScript [code]window[/code]. See [JavaScriptObject] for usage. Prompts the user to download a file containing the specified [code]buffer[/code]. The file will have the given [code]name[/code] and [code]mime[/code] type. [b]Note:[/b] The browser may override the [url=https://en.wikipedia.org/wiki/Media_type]MIME type[/url] provided based on the file [code]name[/code]'s extension. [b]Note:[/b] Browsers might block the download if [method download_buffer] is not being called from a user interaction (e.g. button click). [b]Note:[/b] Browsers might ask the user for permission or block the download if multiple download requests are made in a quick succession. 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. Returns an interface to a JavaScript object that can be used by scripts. The [code]interface[/code] must be a valid property of the JavaScript [code]window[/code]. The callback must accept a single [Array] argument, which will contain the JavaScript [code]arguments[/code]. See [JavaScriptObject] for usage.