Calculate escalating discount using recursion

README.md

calc discount

a recursive function to calculate compounding discount

discount rate: $1.50

gas surcharge: $0.35

stops	discount	cost	per stop
1	$1.50	$8.50	$8.50
2	$3.80	$16.20	$8.10
3	$7.25	$22.75	$7.58
4	$11.85	$28.15	$7.04
5	$17.60	$32.40	$6.48
6	$24.50	$35.50	$5.92

calcdiscount.js

const calc = (stops, discount=1.50, surcharge=0.35) => {
  if (stops <= 0) return 0
  const gasSurcharge = stops > 1 ? stops * surcharge : 0
  return calc(stops - 1, discount, surcharge) + stops * discount - gasSurcharge
}