代码示例:(标识:jsck_prop_element_offsettop_2)
<!DOCTYPE html>
<html>
<head>
<style>
#test {
  left: 100px;
  top: 50px;
  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 的左和上部 offsetTop。</p>
  <p><button onclick="myFunction()">试一试</button></p>
  <p id="demo">offsetLeft: <br>offsetTop: </p>
</div>

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

</body>
</html>
运行结果: