Login to "Debugging Sandbox" environment Find the internal ID of your map/reduce script (not the "script deployment") Page:Script Debugger Choose "API Version 2.0" Click "Switch to Editor" button Paste code snippet below, substitute your script ID into the code block. Click "Debug Script" button. Click the "Play" button (to run the script) Page: Map/Reduce Script Status Code Snippet...

require(['N/task'], function dostuff(task) {

var mrTask = task.create({taskType: task.TaskType.MAP_REDUCE});
mrTask.scriptId = "your_customscript_internalid_goes_here";
mrTask.deploymentId = 1;
var mrTaskId = mrTask.submit();
});