Custom markup in markdown-it

custom_markup.js

var MarkdownIt = require("markdown-it");
var md = new MarkdownIt('commonmark');




// Add custom INLINE rule that pulls in anything wrapped in a ::: <TEXT> ::: and wrap in a span tag 
function custom_inline(state, silent) {
  let pos = state.pos;

  let matchStart = pos;

  let marker = '';
  while (true) {
    let ch = state.src.charCodeAt(pos);
    if (ch !== 0x3A/* : */) {
        break;
    }
    marker += String.fromCharCode(ch);
    pos++;
  }

  if (marker.length < 3) {
      return false;
  }

  let contentStart = pos;
  let contentEnd = state.src.indexOf(marker, pos + marker.length);

  if (contentEnd === -1) {
    return false;
  }

  let matchEnd = contentEnd + marker.length;

  if (!silent) {
    let token;
    token         = state.push('custom_inline', '', 0);
    // token.attrs   = [ [ 'key1', val1 ], [ 'key2', val2] ];
    token.markup  = marker;
    token.content = state.src.slice(contentStart, contentEnd).trim();
  }
  state.pos = matchEnd;
  return true;
}

md.inline.ruler.before('backticks', 'custom_inline', custom_inline);
md.renderer.rules.custom_inline = function (tokens, idx, options, env, self) {
    return  '<span>' + md.utils.escapeHtml(tokens[idx].content) + '</span>';
};





// Add custom BLOCK rule that pulls in anything sandwiched between a startings and ending ::: lines and wraps in a div tag
function getLine(state, lineNum) {
  return state.src.slice(state.bMarks[lineNum], state.eMarks[lineNum]);
}

function custom(state, startLine, endLine, silent) {
  let line;
  let content = [];

  // no whitespace allowed before beginning
  if (state.sCount[startLine] - state.blkIndent > 0) {
    return false;
  }

  // read start marker
  line = getLine(state, startLine);
  let marker = '';
  for (let i = 0; i < line.length; i++) {
    const ch = line.charCodeAt(i);
    if (ch !== 0x3A/* : */) {
        break;
    }
    marker += String.fromCharCode(ch);
  }

  // if no marker found, skip
  if (marker.length < 3) {
    return false;
  }

  // first line must be just the marker
  if (line.indexOf(marker) !== 0 || line.trim() !== marker) {
    return false;
  }

  // keep reading until end marker
  let properlyEnded = false;
  let nextLine = startLine;
  for (nextLine = startLine + 1; nextLine < endLine; nextLine++) {
    line = getLine(state, nextLine);
    if (line.indexOf(marker) === 0 && line.trim() === marker) {
      properlyEnded = true;
      break;
    }

    content.push(line);
  }

  if (!properlyEnded) {
    return false;
  }

  state.line = nextLine + 1;

  if (silent) {
    return true;
  }

  let token;
  token         = state.push('custom', '', 0);
  token.content = content.join('\n');
  token.markup  = marker;
  token.map     = [ startLine, state.line ];

  return true;
}

md.block.ruler.before('fence', 'custom', custom);
md.renderer.rules.custom = function (tokens, idx, options, env, self) {
    return  '<div>' + md.utils.escapeHtml(tokens[idx].content) + '</div>';
};





var result = md.render('# hello!\npooper :::hello1::: ```end```\n\n:::\nhello2\ntest\n\n\ntesttest\n:::\n\n');
console.log(result);

// OUTPUT
// ------
// <h1>hello!</h1>
// <p>pooper <span>hello1</span> <code>end</code></p>
// <div>hello2
// test
// 
//
// testtest</div>