window.onload = function(){

  var a = document.querySelectorAll('.opener'), w = [], url;

  for(i = 0; i < a.length; i++){

    (function(i){

      a[i].onclick = function(e) {

        if (!w[i] || w[i].closed) {

          url = this.href;

          random = Math.floor((Math.random()*100)+1); 

          w[i] = window.open(url, "_blank", random, "menubar=0,scrollbars=0");

        } else {

          console.log('window ' + url + ' is already opened');

        }

        e.preventDefault();

        w[i].focus();

      };

    })(i);

  }

};

​