(function(){

  var originalJqOn = jQuery.fn.on;

  jQuery.fn.extend({

    onAndFirst: function(evtName,fn) {

      fn();

      this.on(evtName, fn);

    }

  });

})();

​

var base = "/act/";

var update_go = function (){

  // in first run "this" equals the global window object

  if (this === window) {

    $('#go').prop('href',base+$("#sel").val());

    console.log("href set to: " + $("#sel").val());

  }

  else {

  $('#go').prop('href',base+$(this).val());

  console.log("href cahnged to: " + base+$(this).val());

  }

};

​

$('#sel').onAndFirst('change',update_go);

​