按钮重复点击解决方法

<button type="button" id="btn">按钮点击</button>
<script type="text/javascript">var btn = document.getElementById("btn");
  var flag = true;
  btn.addEventListener("click",
  function() {
    if (flag) {
      console.log("do sth……");
      flag = false;
      setTimeout(function() {
        flag = true;
      },3000)
    } else {
      console.log("请勿重复点击")
    }
  })
</script>