// in a suitelet
// salesorderIds is an array of strings
task.create({
	taskType: task.TaskType.MAP_REDUCE,
	scriptId: 'customscript_dropship_labels_mr',
	params: {
		custscript_dropship_labels_salesorders: JSON.stringify(salesorderIds)
	}
}).submit();

// in the map/reduce getInputData
var input = runtime.getCurrentScript().getParameter({
	name: 'custscript_dropship_labels_salesorders'
});
var salesorderIds = JSON.parse(input);