function onStarClick(e) {
    if (disabled === true) {
      return;
    }

    if (isRating === true) {
      return;
    }

    if (typeof callback !== "undefined") {
      isRating = true;
      myRating = currentRating;

      if (typeof isBusyText === "undefined") {
        elem.removeAttribute("title");
      } else {
        elem.setAttribute("title", isBusyText);
      }

      elem.classList.add("is-busy");
      callback.call(this, myRating, function () {
        if (disabled === false) {
          elem.removeAttribute("title");
        }

        isRating = false;
        elem.classList.remove("is-busy");
      });
    }
  }
Called when star is clicked.
@param {MouseEvent} e