trycss_position_top 在线代码实例

 <img src="/upload2/attachments/cover/cover_css.png" width="95" height="84" id="img">
  <div>
    <input type="text" value="0" id="num">
    <button id="change">更改top值</button>
    <h1>This is a heading</h1>
  </div>

<script>
  var img = document.getElementById('img');
  var num = document.getElementById('num');
  var btn = document.getElementById('change');
  btn.onclick = function () {
    img.style.top = num.value + 'px';
  }
</script>