javascript - js获取swf播放当前帧一直是0

Question

<embed src='test.swf' width='500px' height='500px' id='swfobj' name='swfobj'></embed>

<script> var currentFrame= document.getElementById('swfobj').CurrentFrame(); </script>

获取到的播放当前帧currentFrame一直为0，这是啥情况