您的jQuery选择器省略了#符号. jQuery ID选择器应该包含如下所示的#:

Your jQuery selector for the form omits the # sign. The jQuery ID selector should include a # like so:

function SubmitForm() {
    $("#UrIntakeForm").valid(); // "#UrIntakeForm" instead of "UrIntakeForm"
 }

否则，您将valid()方法应用于空的jQuery对象，这将导致您指定的错误.

Otherwise you are applying the valid() method to an empty jQuery object, which results with the error you've specified.