var options = { attributes: { rel: 'nofollow', title: 'Click for more information', }, className: 'internal-link', format: { url: function (value) { return value } }, ignoreTags: ['a'], validate: { url: function (value) { return value; } } }; var str = 'Letter From Charles Dow to William Letchworth, 20 February 1908'; document.write(linkifyHtml(str, options));