Something about parsing JSON Back

As we all know, if there is data returned with JSON formatting when doing Ajax requests, we can use JSON.parse() or $.parseJSON() to parse it into a JavaScript object, so that we can easily handle it. However, there are some cases we may need to pay attention to.

Originally, if the request header Content-Type is set with text/plain or text/html, there is no problem with using JSON.parse(). However, when we set it with application/json or text/x-json, do not use JSON.parse() to parse the returned data, as it throws an error.

Despite of this case, we should also focus on using a plugin, named jQuery-File-Upload. According to its official wiki, it has negotiated to Content-Type in IE8/IE9, causing another problem: done handler cannot be triggered when complete uploading, as the following snippet shown:

/** jquery.fileupload.js */
jqXHR = jqXHR || (
    ((aborted || that._trigger(
        'send',
        $.Event('send', {delegatedEvent: e}),
        options
    ) === false) &&
    that._getXHRPromise(false, options.context, aborted)) ||
    that._chunkedUpload(options) || $.ajax(options)
).done(function (result, textStatus, jqXHR) {
    /** cannot be triggered under IE8/IE9 */
    that._onDone(result, textStatus, jqXHR, options);
});

It means that you cannot know when the uploading has been completed. Details has been described in an item of StackOverflow.