New line characters get submitted differently

Question

Hi,

I was wondering if somebody could shed some light on this browser behaviour:

I have a form with a textarea that is submitted to to the server either via XHR (using jQuery, I've also tried with plain XMLHttpRequest just to rule jQuery out and the result is the same) or the "old fashioned" way via form submit. In both cases method="POST" is used. Both ways submit to the same script on the server.

Now the funny part: if you submit via XHR new line characters are transferred as "%0A" (or \n if I am not mistaken), and if you submit the regular way they are transferred as "%0D%0A" (or \r\n). This, off course, causes some problems on the server side, but that is not the question here. I'd just like to know why this difference? Shouldn't new lines be transferred the same no matter what method of submitting you use? What other differences are there (if any)?

Answer 1

In part 3.7.1 of RFC2616(HTTP1.1), it allows either \r\n,\r,\n to represent newline.

HTTP relaxes this requirement and allows the transport of text media with plain CR or LF alone representing a line break when it is done consistently for an entire entity-body. HTTP applications MUST accept CRLF, bare CR, and bare LF as being representative of a line break in text media received via HTTP.

But this does not apply to control structures:

This flexibility regarding line breaks applies only to text media in the entity-body; a bare CR or LF MUST NOT be substituted for CRLF within any of the HTTP control structures (such as header fields and multipart boundaries).

Answer 2

XMLHttpRequest will when sending XML strip the CR characters from the stream. This is in accord with the XML specification which indicates that CRLF be normalised to simple LF.

Hence if you package your content as XML and send it via XHR you will lose the CRs.