我发现了这个问题。

实际问题是，不知怎的，我在页面中有两次jquery包含 - 第二次在页脚，这就是我之前找不到的原因。

Actually the problem was, somehow i got jquery included 2 times in the page - the 2nd time in the footer, that is why I did't find our earlier.

Jquery在页面中只需要一次，它需要在标题中。

Jquery needs to be only 1 time in the page, and it needs to be in the header.