code: function mkdir(dirname, options = {}) {
    if (fs.existsSync(dirname)) return;
    assert.equal(typeof dirname, 'string', 'expected dirname to be a string');
    let opts = Object.assign({ cwd: process.cwd(), fs }, options);
    let mode = opts.mode || 0o777 & ~process.umask();
    let segs = path.relative(opts.cwd, dirname).split(path.sep);
    let make = dir => !exists(dir, opts) && fs.mkdirSync(dir, mode);
    for (let i = 0; i <= segs.length; i++) {
      try {
        make((dirname = path.join(opts.cwd, ...segs.slice(0, i))));
      } catch (err) {
        handleError(dirname, opts)(err);
      }
    }
    return dirname;
  }
docs: Create a directory and any intermediate directories that might exist.