User:Mike.lifeguard/fixCompare.js

Note: After publishing, you may have to bypass your browser's cache to see the changes.

Firefox / Safari: Hold Shift while clicking Reload, or press either Ctrl-F5 or Ctrl-R (⌘-R on a Mac)
Google Chrome: Press Ctrl-Shift-R (⌘-Shift-R on a Mac)
Internet Explorer / Edge: Hold Ctrl while clicking Refresh, or press Ctrl-F5
Opera: Press Ctrl-F5.

//fixcompare.js
//By Superm401
function fixCompare() {
	var histForm=document.getElementsByTagName("form")[1];
	var finalButton=document.getElementById("pagehistory").nextSibling;
	if(!finalButton || finalButton == null) return;
	var firstButton=histForm.getElementsByTagName("input")[1];
	histForm.removeChild(finalButton);
	histForm.removeChild(firstButton);
	var compareLink=document.createElement("a");
	var genLink = mw.config.get('wgServer') + mw.config.get('wgScript') + "?title=" + histForm.title.value + "&diff=" + histForm.diff[0].value + "&oldid=" + histForm.oldid[1].value;
	compareLink.setAttribute("href", genLink);
	compareLink.appendChild(document.createTextNode("Compare selected versions"));
	histForm.insertBefore(compareLink, document.getElementById("pagehistory"));
	var endLink=compareLink.cloneNode(true);
	histForm.appendChild(endLink);
	var diffList=document.getElementById("pagehistory");
	diffList.setAttribute("onchange", "updateCompare()");
}
function updateCompare() {
	var histForm=document.getElementsByTagName("form")[1];
	var diffList=document.getElementById("pagehistory");
	var compareLink=diffList.previousSibling;
	var endLink=diffList.nextSibling;
	var oldInd=-1;
	var i=0;
	while(oldInd==-1 & i<histForm.oldid.length){
		if(histForm.oldid[i].checked)
		oldInd=i;
		i++;
	}
	var diffInd=-1;
	var j=0;
	while(diffInd==-1 & j<histForm.diff.length){
		if(histForm.diff[j].checked)
		diffInd=j;
		j++;
	}
	var genLink = mw.config.get('wgServer') + mw.config.get('wgScript') + "?title=" + histForm.title.value + "&diff=" + histForm.diff[diffInd].value + "&oldid=" + histForm.oldid[oldInd].value;
	compareLink.setAttribute("href", genLink);
	endLink.setAttribute("href", genLink);
}
if( mw.config.get('wgAction') == "history" ) addOnloadHook(fixCompare);