function unquoted(code) {
  if (
    Number.isNaN(code) ||
    code <= codes.space ||
    code === codes.quotationMark ||
    code === codes.apostrophe ||
    code === codes.lessThan ||
    code === codes.equalsTo ||
    code === codes.greaterThan ||
    code === codes.graveAccent ||
    code === codes.rightCurlyBrace
  ) {
    return false
  }

  return true
}
<https://github.com/micromark/micromark-extension-directive/blob/3be1f50/dev/lib/factory-attributes.js#L246>

@param {number} code
@returns {boolean}