i'm able make this work now, the problem earlier is on the csproj file... instead of making the js file as an embeddedresource it was just an included file or something else, my problem now is the extended grouping view's getGroupField method is returning "undefined"


Ext.ux.MultiGroupingView = Ext.extend(Ext.grid.GroupingView, {
    constructor: function(config){
        Ext.ux.MultiGroupingView.superclass.constructor.apply(this, arguments);
        // Added so we can clear cached rows each time the view is refreshed
        this.on("beforerefresh", function() {
            if (this.rowsCache)
                delete rowsCache;
        }, this);
    },
    get_column_by_id: function(id)
    {
        for (i in this.cm.lookup)
        {
            if (this.cm.lookup[i].dataIndex == id)
                return this.cm.lookup[i];
        }
        return null;
    },
    getGroups: function()
    {
        return Ext.DomQuery.select("div.x-grid-group", this.mainBody.dom);
    }
    ,displayEmptyFields: false
    ,displayFieldSeperator: ', '
    ,renderRows: function(){
        var groupField = this.getGroupField();   <--  this is returning "undefined"