How to read column names dynamically.?

How to read column names from source dynamically, to perform some logic on columns.? with out hard-coding each column name in hasOwnProperty(). For example if I have a null values in records, I want those columns to write into separate file.

I don’t know if there is a best practice for this, but one thing you CAN do is run it through a mapper, set to handle null fields, and as pass through, enter EVERY known field as source, and don’t provide a target. That should give you a result that contains NOTHING, but the fields you didn’t specify. Handle null fields apparently only means that it handles source values that don’t exist, EVEN if the field itself doesn’t exist. HOWEVER, if null data DOES exist, it comes across as null.

Thanks stephen, will try implementing the same.