在子菜单页面上保持打开的垂直菜单下拉列表

I've been having trouble trying to wrap my head around how to get my menu sub items to stay open when on the active page. I've seen similar issues with resolutions but I can't seem to get them to work when I implement them, so I do apologise for the question being asked before. I'm using Jquery to open the sub menu items, allowing more than one to be open at any time and also closed at any time, the only issue is when a sub menu item is clicked the menu collapses and i'd like it to stay open when that page is visited. I've attached a JSFiddle to this so you can visualise what my questions is. Thank you, all help is greatly appreciated!I've been having trouble trying to wrap my head