const regex = /((?:<[^>]*>[^<]*?)*?(?:(?!<mark>)<[^>]*(?=>))?)(\W|^)(eiusmod|sort|incididunt|dolor|única|feté)(?=\W|$)/gmu;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('((?:<[^>]*>[^<]*?)*?(?:(?!<mark>)<[^>]*(?=>))?)(\\W|^)(eiusmod|sort|incididunt|dolor|única|feté)(?=\\W|$)', 'gmu')
const str = `única<div data-sort="1">
<p>dolor</p>
<p>única</p>
<h1 data-position="1" eiusmod="foo" >Lorem ipsum dolor sit amet</h1>
<div data="eiusmod"></div>
<strong>search here : consectetur adipiscing elit, </strong>
<div>
sed do <u>eiusmod</u> tempor <mark>incididunt</mark> ut dolor et dolor dolor magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</div>
Duis aute irure <i>dolor</i> dolor in dolor dolor reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
</div>
<div>
sed do <u>eiusmod</u> tempor <mark>incididunt</mark> ut única et única púnica magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</div>
<div>fetén</div>
`;
const subst = `\1\2<mark>\3</mark>`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions