// Assuming N/search is imported as `s`
var mySalesOrderSearch = s.create({
    type: 'salesorder'
    // Use the summary property of a Column to perform grouping/summarizing
    columns: [{
        name: 'salesrep',
        summary: s.Summary.GROUP
    },{
        name: 'internalid',
        summary: s.Summary.COUNT
    }],
    filters: [{
        name: 'mainline',
        operator: 'is',
        values: ['T']
    }]
});

mySalesOrderSearch.run().each(function (result) {
    var repId = result.getValue({
        "name": "salesrep",
        "summary": s.Summary.GROUP
    });
    var repName = result.getText({
        "name": "salesrep",
        "summary": s.Summary.GROUP
    });
    var orderCount = parseInt(result.getValue({
            "name": "internalid",
            "summary": s.Summary.COUNT
    }), 10);

    log.debug({
        "title": "Order Count by Sales Rep",
        "details": repName + " has sold " + orderCount + " orders."
    });
    return true;
});