Quick attempt to convert ansi/vt100 escape sequence to HTML

vt100-to-html.js

let text = "\u001b[H\u001b(B\u001b[mtop - 02:11:23 up 36 days, 18:31,  0 users,  load average: 4.25, 5.34, 5.98\u001b(B\u001b[m\u001b[39;49m\u001b(B\u001b[m\u001b[39;49m\u001b[K\r\n\r\n%Cpu(s):\u001b(B\u001b[m\u001b[39;49m\u001b[1m 21.7 \u001b(B\u001b[m\u001b[39;49;35;43mus,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  8.7 \u001b(B\u001b[m\u001b[39;49msy,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  0.0 \u001b(B\u001b[m\u001b[39;49mni,\u001b(B\u001b[m\u001b[39;49m\u001b[1m 68.3 \u001b(B\u001b[m\u001b[39;49mid,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  0.0 \u001b(B\u001b[m\u001b[39;49mwa,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  0.0 \u001b(B\u001b[m\u001b[39;49mhi,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  1.1 \u001b(B\u001b[m\u001b[39;49msi,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  0.3 \u001b(B\u001b[m\u001b[39;49mst\u001b(B\u001b[m\u001b[39;49m\u001b(B\u001b[m\u001b[39;49m\u001b[K\r\nKiB Mem :\u001b(B\u001b[m\u001b[39;49m\u001b[1m 62916344 \u001b(B\u001b[m\u001b[39;49mtotal,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  3671244 \u001b(B\u001b[m\u001b[39;49mfree,\u001b(B\u001b[m\u001b[39;49m\u001b[1m 39924484 \u001b(B\u001b[m\u001b[39;49mused,\u001b(B\u001b[m\u001b[39;49m\u001b[1m 19320616 \u001b(B\u001b[m\u001b[39;49mbuff/cache\u001b(B\u001b[m\u001b[39;49m\u001b(B\u001b[m\u001b[39;49m\u001b[K\r\nKiB Swap:\u001b(B\u001b[m\u001b[39;49m\u001b[1m 63963132 \u001b(B\u001b[m\u001b[39;49mtotal,\u001b(B\u001b[m\u001b[39;49m\u001b[1m 61726208 \u001b(B\u001b[m\u001b[39;49mfree,\u001b(B\u001b[m\u001b[39;49m\u001b[1m  2236924 \u001b(B\u001b[m\u001b[39;49mused.\u001b(B\u001b[m\u001b[39;49m\u001b[1m 22105164 \u001b(B\u001b[m\u001b[39;49mavail Mem \u001b(B\u001b[m\u001b[39;49m\u001b(B\u001b[m\u001b[39;49m\u001b[K\r\n\u001b[K\r\n\r\n\r\n\r\n\u001b[J\r\n\r\n\u001b[4mHello";

const escSeq = {
  "7": null,
  "8": null,
  "[20h": null,
  "[?1h": null,
  "[?3h": null,
  "[?4h": null,
  "[?5h": null,
  "[?6h": null,
  "[?7h": null,
  "[?8h": null,
  "[?9h": null,
  "[20l": null,
  "[?1l": null,
  "[?2l": null,
  "[?3l": null,
  "[?4l": null,
  "[?5l": null,
  "[?6l": null,
  "[?7l": null,
  "[?8l": null,
  "[?9l": null,
  "=": null,
  ">": null,
  "(A": null,
  ")A": null,
  "(B": null,
  ")B": null,
  "(0": null,
  ")0": null,
  "(1": null,
  ")1": null,
  "(2": null,
  ")2": null,
  "N": null,
  "O": null,
  //   "[m": function (state) { if (state.spanCount > 0) {state.output +=
  // '</span>'; state.spanCount--;} },   "[0m": function (state) { if
  // (state.spanCount > 0) {state.output += '</span>'; state.spanCount--;} },
  // "[1m": { 'class': 'bold' },   "[2m": { 'class': 'light' },   "[4m": {
  // 'class': 'underline' },   "[5m": { 'class': 'blink' },   "[7m": { 'class':
  // 'reverse' },   "[8m": { 'class': 'invisible' },
  "[;r": null,
  "[A": null,
  "[B": null,
  "[C": null,
  "[D": null,
  "[H": null,
  "[;H": null,
  "[f": null,
  "[;f": null,
  "D": null,
  "M": null,
  "E": null,
  "H": null,
  "[g": null,
  "[0g": null,
  "[3g": null,
  "#3": null,
  "#4": null,
  "#5": null,
  "#6": null,
  "[K": null,
  "[0K": null,
  "[1K": null,
  "[2K": null,
  "[J": null,
  "[0J": null,
  "[1J": null,
  "[2J": null,
  "5n": null,
  "0n": null,
  "3n": null,
  "6n": null,
  ";R": null,
  "[c": null,
  "[0c": null,
  "[?1;0c": null,
  "c": null,
  "#8": null,
  "[2;1y": null,
  "[2;2y": null,
  "[2;9y": null,
  "[2;10y": null,
  "[0q": null,
  "[1q": null,
  "[2q": null,
  "[3q": null,
  "[4q": null
}

const modeClasses = {
  '1': 'bold',
  '2': 'light',
  '3': 'underline',
  '4': 'blink',
  '5': 'reverse',
  '6': 'invisible'
}

const modeStyles = {

  '30': 'color: black',
  '31': 'color: red',
  '32': 'color: green',
  '33': 'color: yellow',
  '34': 'color: blue',
  '35': 'color: magenta',
  '36': 'color: cyan',
  '37': 'color: white',

  '40': 'background-color: black',
  '41': 'background-color: red',
  '42': 'background-color: green',
  '43': 'background-color: yellow',
  '44': 'background-color: blue',
  '45': 'background-color: magenta',
  '46': 'background-color: cyan',
  '47': 'background-color: white'
}

function processModes(escapeTxt, state) {
  var modes = escapeTxt.substring(1, escapeTxt.length - 1);

  if (modes.length > 0) {
    modes = modes.split(';');
    for (let i = 0; i < modes.length; i++) {
      if (modeClasses[modes[i]]) {
        state
          .classes
          .push(modeClasses[modes[i]]);
      } else if (modeStyles[modes[i]]) {
        state
          .styles
          .push(modeStyles[modes[i]]);
      }
    }
  } else {
    if (state.spanCount > 0) {
      state.output += '</span>';
      state.spanCount--;
    }
  }
}

function isLetter(str) {
  return str.length === 1 && str.match(/[a-z]/i);
}

function isDigit(str) {
  return str.length === 1 && str.match(/[0-9]/i);
}

function processEscape(escapeTxt, state) {
  if (escapeTxt.startsWith('[') && escapeTxt.endsWith('m')) {
    processModes(escapeTxt, state);
  } else {
    const entry = escSeq[escapeTxt];
    if (entry && entry !== null) {
      if (typeof entry === 'object') {
        if (entry.class) {
          state
            .classes
            .push(entry.class);
        }
        if (entry.style) {
          state
            .styles
            .push(entry.stye);
        }
      } else if (typeof entry === 'function') {
        entry(state);
      }
    }
  }
}

var escapeTxt = '';

var state = {
  output: '',
  spanCount: 0,
  classes: [],
  styles: []
}

for (let i = 0; i < text.length; i++) {
  let character = text.charAt(i);

  if (character === '\u001b') {
    escapeTxt = text.charAt(++i);
    if (escapeTxt === '[') {
      // process until character
      do {
        character = text.charAt(++i)
        escapeTxt += character;
      } while (!isLetter(character) && i < text.length);
    } else if (escapeTxt === '#') {
      // process until digit
      do {
        character = text.charAt(++i)
        escapeTxt += character;
      } while (!isDigit(character) && i < text.length);
    } else if (escapeTxt === '(' || escapeTxt === ')') {
      // process another char
      escapeTxt += text.charAt(++i);
    } else {
      // that's the escape
    }

    processEscape(escapeTxt, state);

  } else {
    if (state.classes.length > 0 || state.styles.length > 0) {
      state.output += `<span class="${state
        .classes
        .join(' ')}" style="${state
        .styles
        .join(';')}">`;
      state.classes = [];
      state.styles = [];
      state.spanCount++;
    }
    state.output += character;
  }
}

if (state.spanCount > 0) {
  for (let i = 0; i < state.spanCount; i++) {
    state.output += '</span>';
  }
}

const styleDefs = '@keyframes blinker { 50% { opacity: 0; } }\n.bold { font-weight: bold; } \n.unde' +
    'rline { text-decoration: underline; } \n.blink { animation: blinker 2s linear in' +
    'finite; } \n.invisible { display: none; } \n';

console.log(`<html><head><style type="text/css">${styleDefs}</style></head><body><pre>${state.output}</pre></body></html>`);

// https://www.csie.ntu.edu.tw/~r92094/c++/VT100.html
// http://www.termsys.demon.co.uk/vtansi.htm
// https://misc.flogisoft.com/bash/tip_colors_and_formatting