Column Expressions: Loop over all columns and create collection

Hi there,

I familiarized with the Column Expressions node and wonder how the Collection option actually works. I.e. I want to loop over all columns like so. It does work but only the last result is given back:

for(let i = 0 ; i < columnNames().length; i++) {
join(columnNames()[i], "=", substr(column(i), 0, 5))
}

In addition, when attempting to create a collection, I get a strange error despite only having strings present:

ERROR Column Expressions   0:2        Execute failed: An error occurred in script 1:
Error occurred during the conversion of the result '@message=96.35' to 'List':
java.lang.String cannot be cast to [Ljava.lang.Object;

hub.knime.com

Thanks in advance

Mike