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Roman Numeral Converter — Arabic ↔ Roman up to 3,999,999

#javascript #webdev #tools #math

Overview

Roman Numeral Converter converts between Arabic numbers and Roman numerals.

🔗 https://devnestio.pages.dev/roman-numeral/

Features

  • Arabic → Roman: supports 1 through 3,999,999
  • Roman → Arabic: validates canonical form with round-trip check
  • Extended range uses vinculum overline notation (MĖ„, DĖ„, CĖ„)
  • Step-by-step breakdown shows each symbol and its contribution
  • 13 click-to-load examples

Algorithm

Greedy subtraction from a lookup table:

const ROMAN_MAP = [
  [1000000,'MĖ„'], [900000,'CĖ„MĖ„'], ..., [900,'CM'], ..., [1,'I']
];
while (rem >= val) { result += sym; rem -= val; }
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Validation uses a round-trip check — re-encode the parsed number and compare with input. This rejects non-canonical forms like IIII or VV automatically.

👉 Try it: https://devnestio.pages.dev/roman-numeral/

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