const regex = /<([^>\s]+)[^>]*>(?:\s*(?:<br \/>| | | | | | | )\s*)*<\/\1>/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('<([^>\\s]+)[^>]*>(?:\\s*(?:<br \\\/>| | | | | | | )\\s*)*<\\\/\\1>', 'gm')
const str = `<div>
<h1>This is a html structure.</h1>
<p>This is not empty.</p>
<p></p>
<p><br /></p>
<p> <br />  </p>
<p> </p>
<p> </p>
</div>`;
const subst = ``;
// 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