How to set a variable to equal current users username?

As the question stated above I am trying to set a variable in my javascript to be the value of the users username. This is how my code is set up:

function submitApproveModal(){ 
  this_file = currentFile;
  
  var approvers = "";
  if(document.getElementById('approvers').checked){
    approvers = '<?php $_SESSION['username'] ?>';
  }
  
  approveFileAjax(this_file.uid, approvers);
}

I know this is not the way for it to work and wondering how exactly can I rewrite my code so that approvers will equal the users username?

>Solution :

You simply forgot the "echo":

approvers = '<?php echo $_SESSION['username'] ?>';

But as mentioned before, mixing up Javascript and PHP is a bad idea.