lib/Ext/DateExtras.js
function xf(format) {
    var args = Array.prototype.slice.call(arguments, 1);
    return format.replace(/\{(\d+)\}/g, function(m, i) {
        return args[i];
    });
}
function xf(format) {
    var args = Array.prototype.slice.call(arguments, 1);
    return format.replace(/\{(\d+)\}/g, function(m, i) {
        return args[i];
    });
}
create private copy of Ext's Ext.util.Format.format() method - to remove unnecessary dependency - to resolve namespace conflict with MS-Ajax's implementation