app/node_modules/markdown-it-deflist/index.js

// Process definition lists
//
'use strict';


module.exports = function deflist_plugin(md) {
  var isSpace = md.utils.isSpace;

  // Search `[:~][\n ]`, returns next pos after marker on success
  // or -1 on fail.
  function skipMarker(state, line) {
    var pos, marker,
        start = state.bMarks[line] + state.tShift[line],
        max = state.eMarks[line];

    if (start >= max) { return -1; }

    // Check bullet
    marker = state.src.charCodeAt(start++);
    if (marker !== 0x7E/* ~ */ && marker !== 0x3A/* : */) { return -1; }

    pos = state.skipSpaces(start);

    // require space after ":"
    if (start === pos) { return -1; }

    // no empty definitions, e.g. "  : "
    if (pos >= max) { return -1; }

    return start;
  }

  function markTightParagraphs(state, idx) {
    var i, l,
        level = state.level + 2;

    for (i = idx + 2, l = state.tokens.length - 2; i < l; i++) {
      if (state.tokens[i].level === level && state.tokens[i].type === 'paragraph_open') {
        state.tokens[i + 2].hidden = true;
        state.tokens[i].hidden = true;
        i += 2;
      }
    }
  }

  function deflist(state, startLine, endLine, silent) {
    var ch,
        contentStart,
        ddLine,
        dtLine,
        itemLines,
        listLines,
        listTokIdx,
        max,
        nextLine,
        offset,
        oldDDIndent,
        oldIndent,
        oldParentType,
        oldSCount,
        oldTShift,
        oldTight,
        pos,
        prevEmptyEnd,
        tight,
        token;

    if (silent) {
      // quirk: validation mode validates a dd block only, not a whole deflist
      if (state.ddIndent < 0) { return false; }
      return skipMarker(state, startLine) >= 0;
    }

    nextLine = startLine + 1;
    if (nextLine >= endLine) { return false; }

    if (state.isEmpty(nextLine)) {
      nextLine++;
      if (nextLine >= endLine) { return false; }
    }

    if (state.sCount[nextLine] < state.blkIndent) { return false; }
    contentStart = skipMarker(state, nextLine);
    if (contentStart < 0) { return false; }

    // Start list
    listTokIdx = state.tokens.length;
    tight = true;

    token     = state.push('dl_open', 'dl', 1);
    token.map = listLines = [ startLine, 0 ];

    //
    // Iterate list items
    //

    dtLine = startLine;
    ddLine = nextLine;

    // One definition list can contain multiple DTs,
    // and one DT can be followed by multiple DDs.
    //
    // Thus, there is two loops here, and label is
    // needed to break out of the second one
    //
    /*eslint no-labels:0,block-scoped-var:0*/
    OUTER:
    for (;;) {
      prevEmptyEnd = false;

      token          = state.push('dt_open', 'dt', 1);
      token.map      = [ dtLine, dtLine ];

      token          = state.push('inline', '', 0);
      token.map      = [ dtLine, dtLine ];
      token.content  = state.getLines(dtLine, dtLine + 1, state.blkIndent, false).trim();
      token.children = [];

      token          = state.push('dt_close', 'dt', -1);

      for (;;) {
        token     = state.push('dd_open', 'dd', 1);
        token.map = itemLines = [ nextLine, 0 ];

        pos = contentStart;
        max = state.eMarks[ddLine];
        offset = state.sCount[ddLine] + contentStart - (state.bMarks[ddLine] + state.tShift[ddLine]);

        while (pos < max) {
          ch = state.src.charCodeAt(pos);

          if (isSpace(ch)) {
            if (ch === 0x09) {
              offset += 4 - offset % 4;
            } else {
              offset++;
            }
          } else {
            break;
          }

          pos++;
        }

        contentStart = pos;

        oldTight = state.tight;
        oldDDIndent = state.ddIndent;
        oldIndent = state.blkIndent;
        oldTShift = state.tShift[ddLine];
        oldSCount = state.sCount[ddLine];
        oldParentType = state.parentType;
        state.blkIndent = state.ddIndent = state.sCount[ddLine] + 2;
        state.tShift[ddLine] = contentStart - state.bMarks[ddLine];
        state.sCount[ddLine] = offset;
        state.tight = true;
        state.parentType = 'deflist';

        state.md.block.tokenize(state, ddLine, endLine, true);

        // If any of list item is tight, mark list as tight
        if (!state.tight || prevEmptyEnd) {
          tight = false;
        }
        // Item become loose if finish with empty line,
        // but we should filter last element, because it means list finish
        prevEmptyEnd = (state.line - ddLine) > 1 && state.isEmpty(state.line - 1);

        state.tShift[ddLine] = oldTShift;
        state.sCount[ddLine] = oldSCount;
        state.tight = oldTight;
        state.parentType = oldParentType;
        state.blkIndent = oldIndent;
        state.ddIndent = oldDDIndent;

        token = state.push('dd_close', 'dd', -1);

        itemLines[1] = nextLine = state.line;

        if (nextLine >= endLine) { break OUTER; }

        if (state.sCount[nextLine] < state.blkIndent) { break OUTER; }
        contentStart = skipMarker(state, nextLine);
        if (contentStart < 0) { break; }

        ddLine = nextLine;

        // go to the next loop iteration:
        // insert DD tag and repeat checking
      }

      if (nextLine >= endLine) { break; }
      dtLine = nextLine;

      if (state.isEmpty(dtLine)) { break; }
      if (state.sCount[dtLine] < state.blkIndent) { break; }

      ddLine = dtLine + 1;
      if (ddLine >= endLine) { break; }
      if (state.isEmpty(ddLine)) { ddLine++; }
      if (ddLine >= endLine) { break; }

      if (state.sCount[ddLine] < state.blkIndent) { break; }
      contentStart = skipMarker(state, ddLine);
      if (contentStart < 0) { break; }

      // go to the next loop iteration:
      // insert DT and DD tags and repeat checking
    }

    // Finilize list
    token = state.push('dl_close', 'dl', -1);

    listLines[1] = nextLine;

    state.line = nextLine;

    // mark paragraphs tight if needed
    if (tight) {
      markTightParagraphs(state, listTokIdx);
    }

    return true;
  }


  md.block.ruler.before('paragraph', 'deflist', deflist, { alt: [ 'paragraph', 'reference', 'blockquote' ] });
};