特定の要素ピカーンと光らせるような感じのもの

下の例だと、指定した要素が一瞬青くなります。

  function flashElement (elem) {
    let indicator = elem.ownerDocument.createElement("div");
    let rect = elem.getBoundingClientRect();
    indicator.id = "nyantoro-element-indicator";
    let style = "background-color: blue; opacity: 0.5; z-index: 999;" +
                "position: fixed; " + 
                "top: " + rect.top + "px;" +
                "height:" + elem.clientHeight + "px;"+
                "left: " + rect.left + "px;" +
                "width: " + elem.clientWidth + "px";
    indicator.setAttribute("style", style);
    elem.appendChild(indicator);
    setTimeout(function () elem.removeChild(indicator), 500);
  }