Check for the existence of fields in a row

The following code examples check for the existence of fields in rows:

var idx = getInputRowMeta().indexOfValue("lookup");
if ( idx < 0 )
{
   var lookupValue = 0;
}
else
{
   var lookupValue = row[idx];
}

With Compatibility mode selected:

var idx = row.searchValueIndex("lookup");
if ( idx < 0 )
{
   var lookupValue = 0;
}
else
{
   var lookupValue = row.getValue(idx);
}

You cannot mix rows in PDI. All rows flowing over a single hop must have the same name, type, and number of fields.