markdown-it/lib/rules_block/heading.js

// heading (#, ##, ...)

'use strict';


module.exports = function heading(state, startLine, endLine, silent) {
  var ch, level, tmp, token,
      pos = state.bMarks[startLine] + state.tShift[startLine],
      max = state.eMarks[startLine];

  ch  = state.src.charCodeAt(pos);

  if (ch !== 0x23/* # */ || pos >= max) { return false; }

  // count heading level
  level = 1;
  ch = state.src.charCodeAt(++pos);
  while (ch === 0x23/* # */ && pos < max && level <= 6) {
    level++;
    ch = state.src.charCodeAt(++pos);
  }

  if (level > 6 || (pos < max && ch !== 0x20/* space */)) { return false; }

  if (silent) { return true; }

  // Let's cut tails like '    ###  ' from the end of string

  max = state.skipCharsBack(max, 0x20, pos); // space
  tmp = state.skipCharsBack(max, 0x23, pos); // #
  if (tmp > pos && state.src.charCodeAt(tmp - 1) === 0x20/* space */) {
    max = tmp;
  }

  state.line = startLine + 1;

  token        = state.push('heading_open', 'h' + String(level), 1);
  token.markup = '########'.slice(0, level);
  token.map    = [ startLine, state.line ];

  token          = state.push('inline', '', 0);
  token.content  = state.src.slice(pos, max).trim();
  token.map      = [ startLine, state.line ];
  token.children = [];

  token        = state.push('heading_close', 'h' + String(level), -1);
  token.markup = '########'.slice(0, level);

  return true;
};