<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<input type="password" id="pass" />
<button id="show-pass" class="" data-password="pass" data-showclass="show" data-hideclass="hide">SHOW</button>

<script>
   $(document).ready(function () {
       $("#show-pass").click(function () {
           var passwordInput = $("#"+$(this).data('password'));
           if( passwordInput.attr('type') === 'password' ){
               passwordInput.attr('type', 'text');
               $(this).removeClass($(this).data('hideclass'));
               $(this).addClass($(this).data('showclass'));
           }else{
               passwordInput.attr('type', 'password');
               $(this).removeClass($(this).data('showclass'));
               $(this).addClass($(this).data('hideclass'));
           }
       });
   });
</script>