In meta:User:Incnis_Mrsi/PDF-PNG.js I used the former for one of the hooks†, whereas pl:MediaWiki:Gadget-edithysteria.js sets a hook with jQuery(document). Which differences exist between one and another?
† The script nowadays fails presumably due to error at $( document ).load( PdfToPNG ), but it’s unclear whether do I attempt something inherently foolish, or anything broke in JS libraries of MediaWiki, or any other kind of error occurred.