JavaScript 中 - 在线编辑器

          <p>改实例使用了 HTML DOM 向 h1 元素添加 "onmouseenter" 和 "onmouseleave" 事件。</p>
<h1 id="demo">Mouse over me</h1>
<script>
  document.getElementById("demo").onmouseenter = function() {
    mouseEnter()
  };
  document.getElementById("demo").onmouseleave = function() {
    mouseLeave()
  };

  function mouseEnter() {
    document.getElementById("demo").style.color = "red";
  }

  function mouseLeave() {
    document.getElementById("demo").style.color = "black";
  }
</script>
        