Updated Converter

src/helper/converter.js

@@ -124,9 +124,55 @@ export default class Converter {
     return romanExpression;
   }
 
+  // fromRoman logic below
+
+  static _extractSeqSameSigns(signs, targetSign, seqIndex) {
+    let result = 0;
+    for (let i = 0; i < this._maxDecimalGroupSigns; i++) {
+      if (signs[seqIndex + i] === targetSign) {
+        result += 1;
+      } else {
+        break;
+      }
+    }
+
+    if (result > this._maxDecimalGroupSigns) {
+      console.error(
+        `Seq row error: should be less than ${this._maxDecimalGroupSigns + 1}`
+      );
+    }
+
+    return result;
+  }
+
   static fromRoman(romanExpression) {
     let result = 0;
-    const signs = romanExpression.split('');
+    const signs = romanExpression.split("");
+
+    for (let seqIndex = 0; seqIndex < signs.length; ) {
+      const currentSign = signs[seqIndex];
+      const upperDictionarySign = this._dictionaryNames[
+        this._dictionaryNames.indexOf(currentSign) - 1
+      ];
+
+      if (upperDictionarySign === signs[seqIndex + 1]) {
+        // records like IX CD CM XL
+        const representChunk =
+          this.Dictionary[upperDictionarySign] - this.Dictionary[currentSign];
+        result += representChunk;
+        seqIndex++;
+      } else {
+        // records like CCC XX III
+        const timesToMultiply = this._extractSeqSameSigns(
+          signs,
+          currentSign,
+          seqIndex
+        );
+        const representChunk = this.Dictionary[currentSign] * timesToMultiply;
+        result += representChunk;
+        seqIndex += timesToMultiply;
+      }
+    }
 
     return result;
   }