const regex = /(?<=<a href=\")([^"]*)-([^&"]*)(?=\.html\">)/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(?<=<a href=\\")([^"]*)-([^&"]*)(?=\\.html\\">)', 'gm')
const str = `<div id="breadcrumb-section">
<ol id="breadcrumbs">
<li class="first">
<span>
<a href="index.html">Technologies</a>
</span>
</li>
<li>
<span>
<a href="Some-Technologies-Documentation_218464400.html">Some Technologies Documentation</a>
</span>
</li>
<li>
<span>
<a href="Some-Other-Documentation_268370090.html">Some Other Documentation</a>
</span>
</li>
<li>
<span>
<a href="Another-Documentation_268370112.html">Another Documentation</a>
</span>
</li>
</ol>
</div>`;
const subst = `$1_$2`;
// 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