Debugging Javascript - General Guidance

We tried with script as below. it works in design mode but not when we call ultra tasks. When we call ultra tasks the script snap doesnt provide any output

execute : function () {
this.log.info(“Executing Transform Script”);
var outDoc = new LinkedHashMap();
var inDoc=null;
var items = new ArrayList();
var i=0;

	while (this.input.hasNext()) 
	{
		try {
			// Read the next input document, store it a new LinkedHashMap, and write this as an output document.
			// We must use a serializable Java type liked LinkedHashMap for each output instead of a native
			// JavaScript object so that downstream Snaps like Copy can process it correctly.
			inDoc = this.input.next();
			i=i+1;
			items.add(inDoc);

			outDoc.put("index", i);         
			
			if ((!this.input.hasNext()) || (this.input.hasNext()==false))
			{   
				outDoc.put("data", items);
				this.output.write(inDoc, outDoc);
			}
			
		}
		catch (err) {
			var errDoc = new LinkedHashMap();
			errDoc.put("error", err);
			this.log.error(err);
			this.error.write(errDoc);
		}
	}
     
    this.log.info("Script executed");