Replace All ใน Javascript

<script type="text/javascript">
 
var str= "Joke";
var oldString = "Hello username! I hope you enjoy Hello your Hello stay username username username.";
 
var newString = oldString .replace(/username/g, str);
 
document.write("Old string =  " + oldString ); 
document.write("<br />New string = " + newString );
 
</script>

Old string = Hello username! I hope you enjoy Hello your Hello stay username username username.
New string = Hello Joke! I hope you enjoy Hello your Hello stay Joke Joke Joke.