<!DOCTYPE html>
<html>
<body>

<p><a id="myAnchor" href="../../www.example.com123@www.example.com/index.html">Example link</a></p>

<p>Click the button to display the username part of the link above.</p>

<button onclick="myFunction()">Try it</button>

<p><b>Note:</b> The username property is not supported in Internet Explorer, Safari and Opera version 12 (and earlier).</p>

<p id="demo"></p>

<script>
function myFunction() {
    var x = document.getElementById("myAnchor").username;
    document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>