I was hoping to get some help with a column renderer. When fired the "this" object refers to the cell view. I was curious to know how I could set the scope to js class.

Thanks for any help

var GridHelper = {
    grid: null,
    dateFormatString: '',

    renderDate: function(value) {
        return Ext.Date.format(value, this.dateFormatString);

    initGrid: function(dateFormatString) {
        this.dateFormatString = dateFormatString;

        this.grid = Ext.create('Ext.grid.GridPanel', {
            id: 'grid',
            columns: [
                    id: "startDateColumn",
                    xtype: "startdatecolumn",
                    text: "Travel Date",
                    renderer: this.renderDate
                    id: "actualStartDateColumn",
                    xtype: "datecolumn",
                    dataIndex: "ActualStartDate",
                    renderer: this.renderDate,
                    text: "Start Date"
                    id: "endDateColumn",
                    xtype: "enddatecolumn",
                    renderer: this.renderDate