I use the Brackets [1] editor. It's free, open source, has a lot of extensions eg: git integration, jshint, .. , supported for many OSes ..
It's based on codemirror, so it may be possible in the future, to get a tiddlywiki syntax highlighter plugin :)
For javascript it has the "edit / view inline"
eg: if you have code like this
$tw.utils.pus][
hTop(classes,this.selectedClass.split(" "));and you want to know how .pushTop() works just place the cursor ][ there and hit <ctrl><e>
It opens the the
exports.pushTop = function(array,value) { .... }source within the active editor. ... That's the best feature of all :)
have fun!
mario
[1]
http://brackets.io/