jquery generateId that preserves existing ids and guesses appropriate prefixes, similar to Ext's id()

generateId.js

$.extend((function() {
    var counts = {};
    return {
        generateId: function(prefix) {
            prefix = (prefix || 'jq') + '-';
            counts[prefix] = counts[prefix] || 0;
            return prefix + counts[prefix]++;
        }
    }
})());
$.fn.generateId = function() {
    return this.each(function() {
        this.id = this.id || $.generateId((this.className.split(' ').shift() || this.tagName.toLowerCase()));
    });
}