The source code

    /**
     * @class Ext.data.SortTypes
     * @singleton
     * Defines the default sorting (casting?) comparison functions used when sorting data.
     */
    Ext.data.SortTypes = {
        /**
         * Default sort that does nothing
         * @param {Mixed} s The value being converted
         * @return {Mixed} The comparison value
         */
        none : function(s){
            return s;
        },

        /**
         * The regular expression used to strip tags
         * @type {RegExp}
         * @property
         */
        stripTagsRE : /<\/?[^>]+>/gi,

        /**
         * Strips all HTML tags to sort on text only
         * @param {Mixed} s The value being converted
         * @return {String} The comparison value
         */
        asText : function(s){
            return String(s).replace(this.stripTagsRE, "");
        },

        /**
         * Strips all HTML tags to sort on text only - Case insensitive
         * @param {Mixed} s The value being converted
         * @return {String} The comparison value
         */
        asUCText : function(s){
            return String(s).toUpperCase().replace(this.stripTagsRE, "");
        },

        /**
         * Case insensitive string
         * @param {Mixed} s The value being converted
         * @return {String} The comparison value
         */
        asUCString : function(s) {
        	return String(s).toUpperCase();
        },

        /**
         * Date sorting
         * @param {Mixed} s The value being converted
         * @return {Number} The comparison value
         */
        asDate : function(s) {
            if(!s){
                return 0;
            }
            if(Ext.isDate(s)){
                return s.getTime();
            }
        	return Date.parse(String(s));
        },

        /**
         * Float sorting
         * @param {Mixed} s The value being converted
         * @return {Float} The comparison value
         */
        asFloat : function(s) {
        	var val = parseFloat(String(s).replace(/,/g, ""));
        	return isNaN(val) ? 0 : val;
        },

        /**
         * Integer sorting
         * @param {Mixed} s The value being converted
         * @return {Number} The comparison value
         */
        asInt : function(s) {
            var val = parseInt(String(s).replace(/,/g, ""), 10);
            return isNaN(val) ? 0 : val;
        }
    };