why encodeURIComponent() for data in body of POST XHR request? - JavaScript / Ajax / DHTML answers

application/x-www-form-urlencoded
This is the same format as a query string, but the string is passed in the request body rather than the URL.

multipart/form-data
This passes the raw, unescaped data in the the POST body by using a marker to define the data boundaries.

why encodeURIComponent() for data in body of POST XHR request? - JavaScript / Ajax / DHTML answers

Because POST uses the same characters to split ('&' and '=') by default. The method doesn't matter; the data is just offered in another part of the request.

GET looks like this (header):

GET /file.html?name=Bart&nr=4 HTTP/1.0

while default POST looks like this (body):

POST /file.html HTTP/1.0
Content-length: 15

name=Bart&nr=4

But the encoding of POST-ed data is only the default behaviour of the browser (which is done in Ajax "by hand" in such libraries).

<form method="post">

actually means:

<form method="post" enctype="application/x-www-form-urlencoded">

But it's possible to disable this URL-encoding for POST-ed data, mostly to transfer (binary) files to the gateway software. In the following example, you tell the form not to encode anything:

<form method="post" enctype="multipart/form-data">

This is the only case where 'é' will be passed as 'é'; under default GET/POST rules it will always be passed as '%E9'.

So as a general conclusion: Ajax libraries must invoke encodeURIComponent() when sending POST-requests in the "application/x-www-form-urlencoded" encoding type. They must always invoke encodeURIComponent() for GET. They must not invoke encodeURIComponent() in the POST "multipart/form-data" type.

Obviously, it also depends on how the gateway software is configured how to handle incoming data (this will be URL decoded by default).

URL-encoding is 'automatic' in browsers as long as you don't override this setting. POST or GET doesn't matter; browser will URL-encode all form values by default before sending them to server.

If you don't want this to happen, you should use

<form method="post" enctype="multipart/form-data">

to receive non-encoded data at server.