For a vcf file containing data for multiple individuals per line, the the vcf on data event returns correct individual names, but the data for each individual is a duplicate of the first individual's data.
To fix this issue, change line 89 in index.js from this:
var formatParts = info[9].split(':')
to this:
var formatParts = info[9 + j].split(':')
The for loop simply needs to loop to each unique individual in each line.