const str = 'Travel <sup style="color:#000;" data-footnote-merchant="1676" data-footnote-index="0" class="sup-comment comm_125">125</sup>Rewards 3000 Loyalty Good and Excellent Credit';
str.replace(/<sup.*?>.*?<\/sup>|(\d+)/g, (m, p1) => p1 ? `<span>${p1}<\/span>` : m);
console.log(str);
Travel <sup style="color:#000;" data-footnote-merchant="1676" data-footnote-index="0" class="sup-comment comm_125">125</sup>Rewards 3000 Loyalty Good and Excellent Credit