JavaScript/Conversions/HexToDecimal.js

function hexToInt (hexNum) {
  const numArr = hexNum.split('') // converts number to array
  return numArr.map((item, index) => {
    switch (item) {
      case 'A': return 10
      case 'B': return 11
      case 'C': return 12
      case 'D': return 13
      case 'E': return 14
      case 'F': return 15
      default: return parseInt(item)
    }
  })
}

function hexToDecimal (hexNum) {
  const intItemsArr = hexToInt(hexNum)
  return intItemsArr.reduce((accumulator, current, index) => {
    return accumulator + (current * Math.pow(16, (intItemsArr.length - (1 + index))))
  }, 0)
}

export { hexToInt, hexToDecimal }