Ext.ux.JSONP for ExtJS 4

Here is a solution for making simple JSONP requests in ExtJS 4

Ext.define('Ext.ux.JSONP', {
    extend: 'Ext.data.ScriptTagProxy',
    alias: 'ux.jsonp',

    createRequestCallback: function(request, operation, callback, scope) {
        var me = this;

        return function(response) {
            callback.apply(scope, [response]);

            operation.setCompleted();
            operation.setSuccessful();
            me.afterRequest(request, true);
        };
    }
});