data
Type: PlainObject or String or Array
Data to be sent to the server. It is converted to a query string, if not already a string. It's appended to the url for GET-requests. See processData option to prevent this automatic processing. Object must be Key/Value pairs. If value is an Array, jQuery serializes multiple values with same key based on the value of the traditional setting (described below).
这段的意思是,最后传给服务端的都是string,但jquery里还可以用key-value对象或者数组,jq会帮你转换。