const values = {

I: 1,

V: 5,

X: 10,

L: 50,

C: 100,

D: 500,

M: 1000

}

export function romanToDecimal (romanNumber) {

let prev = ' '

let sum = 0

let newPrev = 0

for (let i = romanNumber.length - 1; i >= 0; i--) {

const c = romanNumber.charAt(i)

if (prev !== ' ') {

newPrev = values[prev] > newPrev ? values[prev] : newPrev

}

const currentNum = values[c]

if (currentNum >= newPrev) {

sum += currentNum

} else {

sum -= currentNum

}

prev = c

}

return sum

}