Launching Javascript from new tab in firefox

I had a piece of javascript that would take a case id as an argument and open a page on a ticketing tool and to make use of it I created a bookmark in firefox and assigned it to a keyword.

This means I could use the keyword with the case id in the url bar and open up the case directly, similar to setting up proxy bookmark.

However in the versions of firefox I was using, when a new tab was opened it loads a new tab which did not allow me to run javascript.

One solution to this is to change what loads in the new tab, preferably you do not want to load a webpage every time a tab is opened.
To set what to open in the new tab, open about:config, click on the "I'll be careful, I promise!" button and then search for "tab" in the search box.
There should be a setting browser.newtab.url, right click on this and select Modify and enter the url you want to have in each new tab.
As mentioned you don't want this to load a webpage every time, so I use about:blank.

firefox keyword trick

I was wondering if you could add a proxy server as a new custom search to the address bar of firefox and while it is possible for me to write a few lines in a plugin to do this I found another easier way to do this with bookmarks and keywords.

Create a bookmark giving the full url of the proxy server and where you wish to pass the url place %s, give the bookmark a keyword, such as proxy.

Bookmark properties

To use this proxy bookmark, in the address bar type

proxy <url you want to view>