const regex = /<([a-z][a-z0-9]*)(?:[^>]*?((?:\s(?:src|href|style)=['\"][^'\"]*['\"]){0,3}))[^>]*?(\/?)>/ig;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('<([a-z][a-z0-9]*)(?:[^>]*?((?:\\s(?:src|href|style)=[\'\\"][^\'\\"]*[\'\\"]){0,3}))[^>]*?(\\\/?)>', 'ig')
const str = `<title>Hello World</title>
<div style="margin:0px;" href="http://www.google.com" fadeout"="" src="../image.png" >
<img src="abc.jpg" alt="" />
<p style="margin-bottom:10px;">
The event is celebrating its 50th anniversary Kö
<a href="http://www.germany.travel/" style="margin:0px;">exhibition grounds in Cologne</a>.</p>
<p style="padding:0px;"></p>
<p style="color:black;"><strong>A festival for art lovers</strong></p>
</div>`;
const subst = `<$1$2$3>`;
// 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