明明之前好用的代码突然报了这个错误，找了半天发现竟然是导入jquery.min.js 的顺序的问题
Just to be sure this is clear: you cannot put the script reference to jquery-ui before the jquery script itself. That's what fixed the problem to me: first jquery-x.x.x.min.js, then jquery-ui-xxxxxx.js.
把jquery.min.js放到前面就行了。