Bowling game calculator

bowling.js

// Installed npm packages: jquery underscore request express
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/*
  Please write a function to score a game of bowling,
  
  special scoring considerations
  ======================================
  X (strike) => bonus (score from next two throws)
  / (spare) => bonus (score from next throw)
  
  An example game
 |-----|-----|-----|-----|-----|-----|-----|-----|-----|-------|
 | 1 7 | 2 / |  X  |  X  |  X  | 6 / | 7 2 | 1 3 | 4 5 | 1 / 7 |
 |  8  |  28 | 58  |  84 | 104 | 121 | 130 | 134 | 143 | 160   | 
 |-----|-----|-----|-----|-----|-----|-----|-----|-----|-------|
*/

function helper(char, previous) {
	if (char === '/') return 10 - parseInt(previous)
  if (char === 'X') return 10
  return parseInt(char)
}

function score(input) {
  
  const strikeScore = 10;
  const frames = 10
  let final = 0
  
  
  // return final score
  const scoreArray = input.split('')
  
  for (var i=0; i<frames; i = i+2) {
    if (parseInt(scoreArray[i]) + parseInt(scoreArray[i+1]) < 10) {
      // spares and strikes will be skipped here
      final += parseInt(scoreArray[i]) + parseInt(scoreArray[i+1])
    }
    // if scores is a strike advance only by one
    if (scoreArray[i] === 'X') {
      i--;
    }
    
    
    // can only have three max
    final += (
     helper(scoreArray[i], 0) +
     helper(scoreArray[i+1], scoreArray[i]) +
     helper(scoreArray[i+2], scoreArray[i+1])
    )
  }
  return final
}

const input = '172/XXX6/7213451/7'
// score(input) => 160