// Substract 10 business days from 1 September 2014:
var result = subBusinessDays(new Date(2014, 8, 1), 10)
//=> Mon Aug 18 2014 00:00:00 (skipped weekend days)
the amount of business days to be subtracted. Positive decimals will be rounded using Math.floor, decimals less than zero will be rounded using Math.ceil.