Update Lines on Sales Orders using Map/Reduce Script

/**
 *@NApiVersion 2.x
 *@NScriptType MapReduceScript
 */
define(['N/search', 'N/record'], function (search, record) {
    function getInputData() {
        log.debug('START', 'Set Searh');
        //Set search for lines with values you want to change. It is recommended to test the search in UI to see results.
        var inputSearch = search.create({
            type: 'transaction',
                filters: [
            ['mainline', 'is', 'F'], 'and',
            ['type', 'anyof', 'SalesOrd'], 'and',
            ['custcol4', 'contains', 'x']
        ],
            columns: [
            'lineuniquekey' //This field is used to identify particular line
        ]
    });
        //Search result is only for first 1000 lines for more you need implement floating logic or run script multiple times.
        var result = inputSearch.run().getRange({ start: 0, end: 1000 });
        //getInputData step returning results to next step.
        return result;
    }
    function map(context) {
        //Sales order id is set in key and line unique key in value
        context.write({
            key: JSON.parse(context.value).id, //salesorder id as key
                value: JSON.parse(context.value).values.lineuniquekey //line identificators
    });
    }
    //after map step are values reduce to one key = Sales Order id and values array with all lines stored by previous map function
    //in reduce step we execute our logic on records
    function reduce(context) {
        //Loading record, in my case Sales Order and Id is get from context.key (id of SO)
        var recSO = record.load({
            type: 'salesorder',
                id: context.key,
            isDynamic: false
    });
        //Here the script loops through array of lines to be modified.
        var i;
        for (i = 0; i < context.values.length; i++) {
            //looking for number of line with uniqueKey
            var lineNum = recSO.findSublistLineWithValue({
                sublistId: 'item',
                    fieldId: 'lineuniquekey',
                value: context.values[i]
        });
            //update line with new value
            recSO.setSublistValue({
                sublistId: 'item',
                    fieldId: 'custcol4',
                line: lineNum,
                value: 'MapReduced'
        });
        };
        //saving the record
        recSO.save();
        log.debug('saved', 'END');
    }
    function summarize(summary) {
    }
    return {
        getInputData: getInputData,
            map: map,
        reduce: reduce,
        summarize: summarize
}
});