Romain Numeral Addition

number-map.js

const map = {
  1: "I",
  2: "II",
  3: "III",
  4: "IV",
  5: "V",
  6: "VI",
  7: "VII",
  8: "VIII",
  9: "IX",
  10: "X",
  11: "XI",
  12: "XII",
  13: "XIII",
  14: "XIV",
  15: "XV",
  16: "XVI",
  17: "XVII",
  18: "XVIII",
  19: "XIX",
  20: "XX",
  21: "XXI",
  22: "XXII",
  23: "XXIII",
  24: "XXIV",
  25: "XXV",
  26: "XXVI",
  27: "XXVII",
  28: "XXVIII",
  29: "XXIX",
  30: "XXX",
  31: "XXXI",
  32: "XXXII",
  33: "XXXIII",
  34: "XXXIV",
  35: "XXXV",
  36: "XXXVI",
  37: "XXXVII",
  38: "XXXVIII",
  39: "XXXIX",
  40: "XL",
  41: "XLI",
  42: "XLII",
  43: "XLIII",
  44: "XLIV",
  45: "XLV",
  46: "XLVI",
  47: "XLVII",
  48: "XLVIII",
  49: "XLIX",
  50: "L",
  51: "LI",
  52: "LII",
  53: "LIII",
  54: "LIV",
  55: "LV",
  56: "LVI",
  57: "LVII",
  58: "LVIII",
  59: "LIX",
  60: "LX",
  61: "LXI",
  62: "LXII",
  63: "LXIII",
  64: "LXIV",
  65: "LXV",
  66: "LXVI",
  67: "LXVII",
  68: "LXVIII",
  69: "LXIX",
  70: "LXX",
  71: "LXXI",
  72: "LXXII",
  73: "LXXIII",
  74: "LXXIV",
  75: "LXXV",
  76: "LXXVI",
  77: "LXXVII",
  78: "LXXVIII",
  79: "LXXIX",
  80: "LXXX",
  81: "LXXXI",
  82: "LXXXII",
  83: "LXXXIII",
  84: "LXXXIV",
  85: "LXXXV",
  86: "LXXXVI",
  87: "LXXXVII",
  88: "LXXXVIII",
  89: "LXXXIX",
  90: "XC",
  91: "XCI",
  92: "XCII",
  93: "XCIII",
  94: "XCIV",
  95: "XCV",
  96: "XCVI",
  97: "XCVII",
  98: "XCVIII",
  99: "XCIX",
  100: "C",
  101: "CI",
  102: "CII",
  103: "CIII",
  104: "CIV",
  105: "CV",
  106: "CVI",
  107: "CVII",
  108: "CVIII",
  109: "CIX",
  110: "CX",
  111: "CXI",
  112: "CXII",
  113: "CXIII",
  114: "CXIV",
  115: "CXV",
  116: "CXVI",
  117: "CXVII",
  118: "CXVIII",
  119: "CXIX",
  120: "CXX",
  121: "CXXI",
  122: "CXXII",
  123: "CXXIII",
  124: "CXXIV",
  125: "CXXV",
  126: "CXXVI",
  127: "CXXVII",
  128: "CXXVIII",
  129: "CXXIX",
  130: "CXXX",
  131: "CXXXI",
  132: "CXXXII",
  133: "CXXXIII",
  134: "CXXXIV",
  135: "CXXXV",
  136: "CXXXVI",
  137: "CXXXVII",
  138: "CXXXVIII",
  139: "CXXXIX",
  140: "CXL",
  141: "CXLI",
  142: "CXLII",
  143: "CXLIII",
  144: "CXLIV",
  145: "CXLV",
  146: "CXLVI",
  147: "CXLVII",
  148: "CXLVIII",
  149: "CXLIX",
  150: "CL",
  151: "CLI",
  152: "CLII",
  153: "CLIII",
  154: "CLIV",
  155: "CLV",
  156: "CLVI",
  157: "CLVII",
  158: "CLVIII",
  159: "CLIX",
  160: "CLX",
  161: "CLXI",
  162: "CLXII",
  163: "CLXIII",
  164: "CLXIV",
  165: "CLXV",
  166: "CLXVI",
  167: "CLXVII",
  168: "CLXVIII",
  169: "CLXIX",
  170: "CLXX",
  171: "CLXXI",
  172: "CLXXII",
  173: "CLXXIII",
  174: "CLXXIV",
  175: "CLXXV",
  176: "CLXXVI",
  177: "CLXXVII",
  178: "CLXXVIII",
  179: "CLXXIX",
  180: "CLXXX",
  181: "CLXXXI",
  182: "CLXXXII",
  183: "CLXXXIII",
  184: "CLXXXIV",
  185: "CLXXXV",
  186: "CLXXXVI",
  187: "CLXXXVII",
  188: "CLXXXVIII",
  189: "CLXXXIX",
  190: "CXC",
  191: "CXCI",
  192: "CXCII",
  193: "CXCIII",
  194: "CXCIV",
  195: "CXCV",
  196: "CXCVI",
  197: "CXCVII",
  198: "CXCVIII",
  199: "CXCIX",
  200: "CC",
  201: "CCI",
  202: "CCII",
  203: "CCIII",
  204: "CCIV",
  205: "CCV",
  206: "CCVI",
  207: "CCVII",
  208: "CCVIII",
  209: "CCIX",
  210: "CCX",
  211: "CCXI",
  212: "CCXII",
  213: "CCXIII",
  214: "CCXIV",
  215: "CCXV",
  216: "CCXVI",
  217: "CCXVII",
  218: "CCXVIII",
  219: "CCXIX",
  220: "CCXX",
  221: "CCXXI",
  222: "CCXXII",
  223: "CCXXIII",
  224: "CCXXIV",
  225: "CCXXV",
  226: "CCXXVI",
  227: "CCXXVII",
  228: "CCXXVIII",
  229: "CCXXIX",
  230: "CCXXX",
  231: "CCXXXI",
  232: "CCXXXII",
  233: "CCXXXIII",
  234: "CCXXXIV",
  235: "CCXXXV",
  236: "CCXXXVI",
  237: "CCXXXVII",
  238: "CCXXXVIII",
  239: "CCXXXIX",
  240: "CCXL",
  241: "CCXLI",
  242: "CCXLII",
  243: "CCXLIII",
  244: "CCXLIV",
  245: "CCXLV",
  246: "CCXLVI",
  247: "CCXLVII",
  248: "CCXLVIII",
  249: "CCXLIX",
  250: "CCL",
  251: "CCLI",
  252: "CCLII",
  253: "CCLIII",
  254: "CCLIV",
  255: "CCLV",
  256: "CCLVI",
  257: "CCLVII",
  258: "CCLVIII",
  259: "CCLIX",
  260: "CCLX",
  261: "CCLXI",
  262: "CCLXII",
  263: "CCLXIII",
  264: "CCLXIV",
  265: "CCLXV",
  266: "CCLXVI",
  267: "CCLXVII",
  268: "CCLXVIII",
  269: "CCLXIX",
  270: "CCLXX",
  271: "CCLXXI",
  272: "CCLXXII",
  273: "CCLXXIII",
  274: "CCLXXIV",
  275: "CCLXXV",
  276: "CCLXXVI",
  277: "CCLXXVII",
  278: "CCLXXVIII",
  279: "CCLXXIX",
  280: "CCLXXX",
  281: "CCLXXXI",
  282: "CCLXXXII",
  283: "CCLXXXIII",
  284: "CCLXXXIV",
  285: "CCLXXXV",
  286: "CCLXXXVI",
  287: "CCLXXXVII",
  288: "CCLXXXVIII",
  289: "CCLXXXIX",
  290: "CCXC",
  291: "CCXCI",
  292: "CCXCII",
  293: "CCXCIII",
  294: "CCXCIV",
  295: "CCXCV",
  296: "CCXCVI",
  297: "CCXCVII",
  298: "CCXCVIII",
  299: "CCXCIX",
  300: "CCC",
  301: "CCCI",
  302: "CCCII",
  303: "CCCIII",
  304: "CCCIV",
  305: "CCCV",
  306: "CCCVI",
  307: "CCCVII",
  308: "CCCVIII",
  309: "CCCIX",
  310: "CCCX",
  311: "CCCXI",
  312: "CCCXII",
  313: "CCCXIII",
  314: "CCCXIV",
  315: "CCCXV",
  316: "CCCXVI",
  317: "CCCXVII",
  318: "CCCXVIII",
  319: "CCCXIX",
  320: "CCCXX",
  321: "CCCXXI",
  322: "CCCXXII",
  323: "CCCXXIII",
  324: "CCCXXIV",
  325: "CCCXXV",
  326: "CCCXXVI",
  327: "CCCXXVII",
  328: "CCCXXVIII",
  329: "CCCXXIX",
  330: "CCCXXX",
  331: "CCCXXXI",
  332: "CCCXXXII",
  333: "CCCXXXIII",
  334: "CCCXXXIV",
  335: "CCCXXXV",
  336: "CCCXXXVI",
  337: "CCCXXXVII",
  338: "CCCXXXVIII",
  339: "CCCXXXIX",
  340: "CCCXL",
  341: "CCCXLI",
  342: "CCCXLII",
  343: "CCCXLIII",
  344: "CCCXLIV",
  345: "CCCXLV",
  346: "CCCXLVI",
  347: "CCCXLVII",
  348: "CCCXLVIII",
  349: "CCCXLIX",
  350: "CCCL",
  351: "CCCLI",
  352: "CCCLII",
  353: "CCCLIII",
  354: "CCCLIV",
  355: "CCCLV",
  356: "CCCLVI",
  357: "CCCLVII",
  358: "CCCLVIII",
  359: "CCCLIX",
  360: "CCCLX",
  361: "CCCLXI",
  362: "CCCLXII",
  363: "CCCLXIII",
  364: "CCCLXIV",
  365: "CCCLXV",
  366: "CCCLXVI",
  367: "CCCLXVII",
  368: "CCCLXVIII",
  369: "CCCLXIX",
  370: "CCCLXX",
  371: "CCCLXXI",
  372: "CCCLXXII",
  373: "CCCLXXIII",
  374: "CCCLXXIV",
  375: "CCCLXXV",
  376: "CCCLXXVI",
  377: "CCCLXXVII",
  378: "CCCLXXVIII",
  379: "CCCLXXIX",
  380: "CCCLXXX",
  381: "CCCLXXXI",
  382: "CCCLXXXII",
  383: "CCCLXXXIII",
  384: "CCCLXXXIV",
  385: "CCCLXXXV",
  386: "CCCLXXXVI",
  387: "CCCLXXXVII",
  388: "CCCLXXXVIII",
  389: "CCCLXXXIX",
  390: "CCCXC",
  391: "CCCXCI",
  392: "CCCXCII",
  393: "CCCXCIII",
  394: "CCCXCIV",
  395: "CCCXCV",
  396: "CCCXCVI",
  397: "CCCXCVII",
  398: "CCCXCVIII",
  399: "CCCXCIX",
  400: "CD",
  401: "CDI",
  402: "CDII",
  403: "CDIII",
  404: "CDIV",
  405: "CDV",
  406: "CDVI",
  407: "CDVII",
  408: "CDVIII",
  409: "CDIX",
  410: "CDX",
  411: "CDXI",
  412: "CDXII",
  413: "CDXIII",
  414: "CDXIV",
  415: "CDXV",
  416: "CDXVI",
  417: "CDXVII",
  418: "CDXVIII",
  419: "CDXIX",
  420: "CDXX",
  421: "CDXXI",
  422: "CDXXII",
  423: "CDXXIII",
  424: "CDXXIV",
  425: "CDXXV",
  426: "CDXXVI",
  427: "CDXXVII",
  428: "CDXXVIII",
  429: "CDXXIX",
  430: "CDXXX",
  431: "CDXXXI",
  432: "CDXXXII",
  433: "CDXXXIII",
  434: "CDXXXIV",
  435: "CDXXXV",
  436: "CDXXXVI",
  437: "CDXXXVII",
  438: "CDXXXVIII",
  439: "CDXXXIX",
  440: "CDXL",
  441: "CDXLI",
  442: "CDXLII",
  443: "CDXLIII",
  444: "CDXLIV",
  445: "CDXLV",
  446: "CDXLVI",
  447: "CDXLVII",
  448: "CDXLVIII",
  449: "CDXLIX",
  450: "CDL",
  451: "CDLI",
  452: "CDLII",
  453: "CDLIII",
  454: "CDLIV",
  455: "CDLV",
  456: "CDLVI",
  457: "CDLVII",
  458: "CDLVIII",
  459: "CDLIX",
  460: "CDLX",
  461: "CDLXI",
  462: "CDLXII",
  463: "CDLXIII",
  464: "CDLXIV",
  465: "CDLXV",
  466: "CDLXVI",
  467: "CDLXVII",
  468: "CDLXVIII",
  469: "CDLXIX",
  470: "CDLXX",
  471: "CDLXXI",
  472: "CDLXXII",
  473: "CDLXXIII",
  474: "CDLXXIV",
  475: "CDLXXV",
  476: "CDLXXVI",
  477: "CDLXXVII",
  478: "CDLXXVIII",
  479: "CDLXXIX",
  480: "CDLXXX",
  481: "CDLXXXI",
  482: "CDLXXXII",
  483: "CDLXXXIII",
  484: "CDLXXXIV",
  485: "CDLXXXV",
  486: "CDLXXXVI",
  487: "CDLXXXVII",
  488: "CDLXXXVIII",
  489: "CDLXXXIX",
  490: "CDXC",
  491: "CDXCI",
  492: "CDXCII",
  493: "CDXCIII",
  494: "CDXCIV",
  495: "CDXCV",
  496: "CDXCVI",
  497: "CDXCVII",
  498: "CDXCVIII",
  499: "CDXCIX",
  500: "D",
  501: "DI",
  502: "DII",
  503: "DIII",
  504: "DIV",
  505: "DV",
  506: "DVI",
  507: "DVII",
  508: "DVIII",
  509: "DIX",
  510: "DX",
  511: "DXI",
  512: "DXII",
  513: "DXIII",
  514: "DXIV",
  515: "DXV",
  516: "DXVI",
  517: "DXVII",
  518: "DXVIII",
  519: "DXIX",
  520: "DXX",
  521: "DXXI",
  522: "DXXII",
  523: "DXXIII",
  524: "DXXIV",
  525: "DXXV",
  526: "DXXVI",
  527: "DXXVII",
  528: "DXXVIII",
  529: "DXXIX",
  530: "DXXX",
  531: "DXXXI",
  532: "DXXXII",
  533: "DXXXIII",
  534: "DXXXIV",
  535: "DXXXV",
  536: "DXXXVI",
  537: "DXXXVII",
  538: "DXXXVIII",
  539: "DXXXIX",
  540: "DXL",
  541: "DXLI",
  542: "DXLII",
  543: "DXLIII",
  544: "DXLIV",
  545: "DXLV",
  546: "DXLVI",
  547: "DXLVII",
  548: "DXLVIII",
  549: "DXLIX",
  550: "DL",
  551: "DLI",
  552: "DLII",
  553: "DLIII",
  554: "DLIV",
  555: "DLV",
  556: "DLVI",
  557: "DLVII",
  558: "DLVIII",
  559: "DLIX",
  560: "DLX",
  561: "DLXI",
  562: "DLXII",
  563: "DLXIII",
  564: "DLXIV",
  565: "DLXV",
  566: "DLXVI",
  567: "DLXVII",
  568: "DLXVIII",
  569: "DLXIX",
  570: "DLXX",
  571: "DLXXI",
  572: "DLXXII",
  573: "DLXXIII",
  574: "DLXXIV",
  575: "DLXXV",
  576: "DLXXVI",
  577: "DLXXVII",
  578: "DLXXVIII",
  579: "DLXXIX",
  580: "DLXXX",
  581: "DLXXXI",
  582: "DLXXXII",
  583: "DLXXXIII",
  584: "DLXXXIV",
  585: "DLXXXV",
  586: "DLXXXVI",
  587: "DLXXXVII",
  588: "DLXXXVIII",
  589: "DLXXXIX",
  590: "DXC",
  591: "DXCI",
  592: "DXCII",
  593: "DXCIII",
  594: "DXCIV",
  595: "DXCV",
  596: "DXCVI",
  597: "DXCVII",
  598: "DXCVIII",
  599: "DXCIX",
  600: "DC",
  601: "DCI",
  602: "DCII",
  603: "DCIII",
  604: "DCIV",
  605: "DCV",
  606: "DCVI",
  607: "DCVII",
  608: "DCVIII",
  609: "DCIX",
  610: "DCX",
  611: "DCXI",
  612: "DCXII",
  613: "DCXIII",
  614: "DCXIV",
  615: "DCXV",
  616: "DCXVI",
  617: "DCXVII",
  618: "DCXVIII",
  619: "DCXIX",
  620: "DCXX",
  621: "DCXXI",
  622: "DCXXII",
  623: "DCXXIII",
  624: "DCXXIV",
  625: "DCXXV",
  626: "DCXXVI",
  627: "DCXXVII",
  628: "DCXXVIII",
  629: "DCXXIX",
  630: "DCXXX",
  631: "DCXXXI",
  632: "DCXXXII",
  633: "DCXXXIII",
  634: "DCXXXIV",
  635: "DCXXXV",
  636: "DCXXXVI",
  637: "DCXXXVII",
  638: "DCXXXVIII",
  639: "DCXXXIX",
  640: "DCXL",
  641: "DCXLI",
  642: "DCXLII",
  643: "DCXLIII",
  644: "DCXLIV",
  645: "DCXLV",
  646: "DCXLVI",
  647: "DCXLVII",
  648: "DCXLVIII",
  649: "DCXLIX",
  650: "DCL",
  651: "DCLI",
  652: "DCLII",
  653: "DCLIII",
  654: "DCLIV",
  655: "DCLV",
  656: "DCLVI",
  657: "DCLVII",
  658: "DCLVIII",
  659: "DCLIX",
  660: "DCLX",
  661: "DCLXI",
  662: "DCLXII",
  663: "DCLXIII",
  664: "DCLXIV",
  665: "DCLXV",
  666: "DCLXVI",
  667: "DCLXVII",
  668: "DCLXVIII",
  669: "DCLXIX",
  670: "DCLXX",
  671: "DCLXXI",
  672: "DCLXXII",
  673: "DCLXXIII",
  674: "DCLXXIV",
  675: "DCLXXV",
  676: "DCLXXVI",
  677: "DCLXXVII",
  678: "DCLXXVIII",
  679: "DCLXXIX",
  680: "DCLXXX",
  681: "DCLXXXI",
  682: "DCLXXXII",
  683: "DCLXXXIII",
  684: "DCLXXXIV",
  685: "DCLXXXV",
  686: "DCLXXXVI",
  687: "DCLXXXVII",
  688: "DCLXXXVIII",
  689: "DCLXXXIX",
  690: "DCXC",
  691: "DCXCI",
  692: "DCXCII",
  693: "DCXCIII",
  694: "DCXCIV",
  695: "DCXCV",
  696: "DCXCVI",
  697: "DCXCVII",
  698: "DCXCVIII",
  699: "DCXCIX",
  700: "DCC",
  701: "DCCI",
  702: "DCCII",
  703: "DCCIII",
  704: "DCCIV",
  705: "DCCV",
  706: "DCCVI",
  707: "DCCVII",
  708: "DCCVIII",
  709: "DCCIX",
  710: "DCCX",
  711: "DCCXI",
  712: "DCCXII",
  713: "DCCXIII",
  714: "DCCXIV",
  715: "DCCXV",
  716: "DCCXVI",
  717: "DCCXVII",
  718: "DCCXVIII",
  719: "DCCXIX",
  720: "DCCXX",
  721: "DCCXXI",
  722: "DCCXXII",
  723: "DCCXXIII",
  724: "DCCXXIV",
  725: "DCCXXV",
  726: "DCCXXVI",
  727: "DCCXXVII",
  728: "DCCXXVIII",
  729: "DCCXXIX",
  730: "DCCXXX",
  731: "DCCXXXI",
  732: "DCCXXXII",
  733: "DCCXXXIII",
  734: "DCCXXXIV",
  735: "DCCXXXV",
  736: "DCCXXXVI",
  737: "DCCXXXVII",
  738: "DCCXXXVIII",
  739: "DCCXXXIX",
  740: "DCCXL",
  741: "DCCXLI",
  742: "DCCXLII",
  743: "DCCXLIII",
  744: "DCCXLIV",
  745: "DCCXLV",
  746: "DCCXLVI",
  747: "DCCXLVII",
  748: "DCCXLVIII",
  749: "DCCXLIX",
  750: "DCCL",
  751: "DCCLI",
  752: "DCCLII",
  753: "DCCLIII",
  754: "DCCLIV",
  755: "DCCLV",
  756: "DCCLVI",
  757: "DCCLVII",
  758: "DCCLVIII",
  759: "DCCLIX",
  760: "DCCLX",
  761: "DCCLXI",
  762: "DCCLXII",
  763: "DCCLXIII",
  764: "DCCLXIV",
  765: "DCCLXV",
  766: "DCCLXVI",
  767: "DCCLXVII",
  768: "DCCLXVIII",
  769: "DCCLXIX",
  770: "DCCLXX",
  771: "DCCLXXI",
  772: "DCCLXXII",
  773: "DCCLXXIII",
  774: "DCCLXXIV",
  775: "DCCLXXV",
  776: "DCCLXXVI",
  777: "DCCLXXVII",
  778: "DCCLXXVIII",
  779: "DCCLXXIX",
  780: "DCCLXXX",
  781: "DCCLXXXI",
  782: "DCCLXXXII",
  783: "DCCLXXXIII",
  784: "DCCLXXXIV",
  785: "DCCLXXXV",
  786: "DCCLXXXVI",
  787: "DCCLXXXVII",
  788: "DCCLXXXVIII",
  789: "DCCLXXXIX",
  790: "DCCXC",
  791: "DCCXCI",
  792: "DCCXCII",
  793: "DCCXCIII",
  794: "DCCXCIV",
  795: "DCCXCV",
  796: "DCCXCVI",
  797: "DCCXCVII",
  798: "DCCXCVIII",
  799: "DCCXCIX",
  800: "DCCC",
  801: "DCCCI",
  802: "DCCCII",
  803: "DCCCIII",
  804: "DCCCIV",
  805: "DCCCV",
  806: "DCCCVI",
  807: "DCCCVII",
  808: "DCCCVIII",
  809: "DCCCIX",
  810: "DCCCX",
  811: "DCCCXI",
  812: "DCCCXII",
  813: "DCCCXIII",
  814: "DCCCXIV",
  815: "DCCCXV",
  816: "DCCCXVI",
  817: "DCCCXVII",
  818: "DCCCXVIII",
  819: "DCCCXIX",
  820: "DCCCXX",
  821: "DCCCXXI",
  822: "DCCCXXII",
  823: "DCCCXXIII",
  824: "DCCCXXIV",
  825: "DCCCXXV",
  826: "DCCCXXVI",
  827: "DCCCXXVII",
  828: "DCCCXXVIII",
  829: "DCCCXXIX",
  830: "DCCCXXX",
  831: "DCCCXXXI",
  832: "DCCCXXXII",
  833: "DCCCXXXIII",
  834: "DCCCXXXIV",
  835: "DCCCXXXV",
  836: "DCCCXXXVI",
  837: "DCCCXXXVII",
  838: "DCCCXXXVIII",
  839: "DCCCXXXIX",
  840: "DCCCXL",
  841: "DCCCXLI",
  842: "DCCCXLII",
  843: "DCCCXLIII",
  844: "DCCCXLIV",
  845: "DCCCXLV",
  846: "DCCCXLVI",
  847: "DCCCXLVII",
  848: "DCCCXLVIII",
  849: "DCCCXLIX",
  850: "DCCCL",
  851: "DCCCLI",
  852: "DCCCLII",
  853: "DCCCLIII",
  854: "DCCCLIV",
  855: "DCCCLV",
  856: "DCCCLVI",
  857: "DCCCLVII",
  858: "DCCCLVIII",
  859: "DCCCLIX",
  860: "DCCCLX",
  861: "DCCCLXI",
  862: "DCCCLXII",
  863: "DCCCLXIII",
  864: "DCCCLXIV",
  865: "DCCCLXV",
  866: "DCCCLXVI",
  867: "DCCCLXVII",
  868: "DCCCLXVIII",
  869: "DCCCLXIX",
  870: "DCCCLXX",
  871: "DCCCLXXI",
  872: "DCCCLXXII",
  873: "DCCCLXXIII",
  874: "DCCCLXXIV",
  875: "DCCCLXXV",
  876: "DCCCLXXVI",
  877: "DCCCLXXVII",
  878: "DCCCLXXVIII",
  879: "DCCCLXXIX",
  880: "DCCCLXXX",
  881: "DCCCLXXXI",
  882: "DCCCLXXXII",
  883: "DCCCLXXXIII",
  884: "DCCCLXXXIV",
  885: "DCCCLXXXV",
  886: "DCCCLXXXVI",
  887: "DCCCLXXXVII",
  888: "DCCCLXXXVIII",
  889: "DCCCLXXXIX",
  890: "DCCCXC",
  891: "DCCCXCI",
  892: "DCCCXCII",
  893: "DCCCXCIII",
  894: "DCCCXCIV",
  895: "DCCCXCV",
  896: "DCCCXCVI",
  897: "DCCCXCVII",
  898: "DCCCXCVIII",
  899: "DCCCXCIX",
  900: "CM",
  901: "CMI",
  902: "CMII",
  903: "CMIII",
  904: "CMIV",
  905: "CMV",
  906: "CMVI",
  907: "CMVII",
  908: "CMVIII",
  909: "CMIX",
  910: "CMX",
  911: "CMXI",
  912: "CMXII",
  913: "CMXIII",
  914: "CMXIV",
  915: "CMXV",
  916: "CMXVI",
  917: "CMXVII",
  918: "CMXVIII",
  919: "CMXIX",
  920: "CMXX",
  921: "CMXXI",
  922: "CMXXII",
  923: "CMXXIII",
  924: "CMXXIV",
  925: "CMXXV",
  926: "CMXXVI",
  927: "CMXXVII",
  928: "CMXXVIII",
  929: "CMXXIX",
  930: "CMXXX",
  931: "CMXXXI",
  932: "CMXXXII",
  933: "CMXXXIII",
  934: "CMXXXIV",
  935: "CMXXXV",
  936: "CMXXXVI",
  937: "CMXXXVII",
  938: "CMXXXVIII",
  939: "CMXXXIX",
  940: "CMXL",
  941: "CMXLI",
  942: "CMXLII",
  943: "CMXLIII",
  944: "CMXLIV",
  945: "CMXLV",
  946: "CMXLVI",
  947: "CMXLVII",
  948: "CMXLVIII",
  949: "CMXLIX",
  950: "CML",
  951: "CMLI",
  952: "CMLII",
  953: "CMLIII",
  954: "CMLIV",
  955: "CMLV",
  956: "CMLVI",
  957: "CMLVII",
  958: "CMLVIII",
  959: "CMLIX",
  960: "CMLX",
  961: "CMLXI",
  962: "CMLXII",
  963: "CMLXIII",
  964: "CMLXIV",
  965: "CMLXV",
  966: "CMLXVI",
  967: "CMLXVII",
  968: "CMLXVIII",
  969: "CMLXIX",
  970: "CMLXX",
  971: "CMLXXI",
  972: "CMLXXII",
  973: "CMLXXIII",
  974: "CMLXXIV",
  975: "CMLXXV",
  976: "CMLXXVI",
  977: "CMLXXVII",
  978: "CMLXXVIII",
  979: "CMLXXIX",
  980: "CMLXXX",
  981: "CMLXXXI",
  982: "CMLXXXII",
  983: "CMLXXXIII",
  984: "CMLXXXIV",
  985: "CMLXXXV",
  986: "CMLXXXVI",
  987: "CMLXXXVII",
  988: "CMLXXXVIII",
  989: "CMLXXXIX",
  990: "CMXC",
  991: "CMXCI",
  992: "CMXCII",
  993: "CMXCIII",
  994: "CMXCIV",
  995: "CMXCV",
  996: "CMXCVI",
  997: "CMXCVII",
  998: "CMXCVIII",
  999: "CMXCIX",
  1000: "M",
};

module.exports = map;

roman-numeral-addition.js

const assert = require("assert");
const numbers = require("./number-map");

function numeralAddition(addendA, addendB) {
  // addendA should be bigger
  if (addendB.length > addendA.length) {
    [addendA, addendB] = [addendB, addendA];
  }

  let result = addendA;
  let pointer = "";

  while (pointer != addendB) {
    result = increment(result);
    pointer = increment(pointer);
  }

  return result;
}

function increment(num) {
  let result = num + "I";

  // pattern 1: two units away: IXI => X, XCX => C
  result = replaceCurrAndNext(
    result,
    (c, n) => new RegExp(`${c}${next(n)}${c}$`),
    (_, n) => next(n)
  );

  // pattern 2: one unit away: IVI => V, XLX => L
  result = replaceCurrAndNext(
    result,
    (c, n) => new RegExp(`${c}${n}${c}$`),
    (_, n) => n
  );

  // pattern 3: four units: IIII => IV, XXXX => XL, CCCC => CD
  result = result.replace(
    /(I|X|C)(\1{3})/,
    (_, captureGroup1) => captureGroup1 + next(captureGroup1)
  );

  // pattern 4: one unit away inverted, to two units away: VIV => IX, LXL => XC
  result = replaceCurrAndNext(
    result,
    (c, n) => new RegExp(`${n}${c}${n}$`),
    (c, n) => `${c}${next(n)}`
  );

  return result;
}

function next(unit) {
  const units = "IVXLCDM".split("");
  const idx = units.indexOf(unit);
  return idx > -1 && units[idx + 1] ? units[idx + 1] : null;
}

function replaceCurrAndNext(result, getRegex, getReplacement) {
  let currUnit = "I";
  while (currUnit) {
    const nextUnit = next(currUnit);

    if (nextUnit) {
      result = result.replace(
        getRegex(currUnit, nextUnit),
        getReplacement(currUnit, nextUnit)
      );
    }

    currUnit = nextUnit;
  }

  return result;
}

// ===== TEST =====

const done = {};

const MAX = 1000;
for (let i = 1; i <= MAX; i++) {
  const addendA = numbers[i];
  console.log(addendA);

  for (let j = 1; j <= MAX; j++) {
    if (i + j > MAX) continue; // no answer available in map
    const addendB = numbers[j];

    if (done[[addendA, addendB].join("+")]) continue; // previously tested
    done[[addendA, addendB].join("+")] = true;
    done[[addendB, addendA].join("+")] = true;

    const expected = numbers[i + j];

    const result = numeralAddition(addendA, addendB);

    assert.equal(result, expected, `${addendA} + ${addendB} should equal ${expected}`);
  }
}

console.log("done!");