Yes. So would sugar.js's escapeHTML: http://sugarjs.com/api/String/escapeHTML.
I'm bah-leting this function. It ended up being unused anywho.
Thanks for the reminder about Ext.util -- I had gotten into a habit of stopping my search through Ext docs if I didn't find something general purpose in the top-level Ext class methods... Ext.each, Ext.urlEncode etc.