jQuery.fn.maxchars = function( max ) {

  var elem = $( this );
  var len = elem.val().length;

  elem
    .parent().after( "<label><span class=\"maxchars\">" + len + " / " + max + "</span></label>")
    .keyup( function() {

      var len = elem.val().length;

      elem.parent().next().children( ".maxchars" ).html( len + " / " + max );

      if( len > max ) {
        elem.val( elem.val().substring( 0, max ) );
      }

  } );

  return this;

};