function purge() {//Here, we declare the function and its parameters
var hist; var url;//Here, we declare two variables
if (!(hist = document.getElementById('ca-history') )) return; //Try to set hist as the document's element
//with id 'ca-history' - tha's the history tab
if (!(url = hist.getElementsByTagName('a')[0] )) return; //Try to set url as the history tab's first
//element with the tag 'a'
if (!(url = url.href )) return; //Try to set url as the href of that element from line 3
mw.util.addPortletLink('p-cactions', //add a PortletLink to the p-cactions area (the tabs at the top of the page)
url.replace(/([?&]action=)history([&#]|$)/, '$1purge$2'), //replace the ?action=history
//part of the href we got from
//the history tab with ?action=purge,
//and set it as the destination
'purge', //set the text that will appear on the tab
'ca-purge', //set the internal id for the tab - this is useful for
//referring to it, and positioning tabs relative to one another
'Purge server cache for this page', //set the mouseover text
'0'); //the access key
}
if ( wgCanonicalNamespace != "Special" ) addOnloadHook(purge); //if it's not a special page then hook onto the page loading
//and run the function purge
