html运行实例（jsck_prop_element_offsettop

代码示例：（标识：jsck_prop_element_offsettop_1）

<!DOCTYPE html>
<html>
<head>
<style>
#test {
  top: 100px;
  margin: 10px;
  padding: 10px;
  width: 300px;
  position: relative;
  border: 5px solid black
}
</style>
</head>
<body>

<div id="test">
  <p>点击按钮可获取 test div 的 offsetTop。</p>
  <p><button onclick="myFunction()">试一试</button></p>
  <p>offsetTop is: <span id="demo"></span></p>
</div>

<script>
function myFunction() {
  var testDiv = document.getElementById("test");
  document.getElementById("demo").innerHTML = testDiv.offsetTop;
}
</script>

</body>
</html>