Create RomanToDecimal.js

Conversion from Roman numeral system to decimal

Conversions/RomanToDecimal.js

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+var values = {
+  'I':1,
+  'V':5,
+  'X':10,
+  'L':50,
+  'C':100,
+  'D':500,
+  'M':1000
+};
+
+function romanToDecimal(romanNumber){
+  let prev = ' ';
+
+  let sum = 0;
+
+  let newPrev = 0;
+  for(let i = romanNumber.length - 1; i >= 0; i--){
+    let c = romanNumber.charAt(i);
+
+    if(prev !== ' '){
+      newPrev = values[prev] > newPrev ? values[prev] : newPrev;
+    }
+
+    let currentNum = values[c];
+    if(currentNum >= newPrev){
+      sum += currentNum;
+    } else {
+      sum -= currentNum;
+    }
+    
+    prev = c;
+  }
+  return sum;
+}
+
+console.log(romanToDecimal('XXIIVV'));
+console.log(romanToDecimal('MDCCCIV'));
+console.log(romanToDecimal('XXIVI'));