Please reopen and attach a test case.

add below js in a html file

var parms_str = "ab+ba";

var paramResult = $.param(parms_str, false);

alert(paramResult);

var deObj = $.deparam(paramResult, false);

var deObj2 = $.deparam("ab ba", false);

alert(deObj);

alert(deObj2);

you can see alert deObj shows "ab ba" instead of "ab+ba"

actuall this might be clearer, in ajax function, jQuery does

// convert data if not already a string

if ( s.data && s.processData && typeof s.data !== "string" ) {

s.data = jQuery.param( s.data, s.traditional );

}

so string input is not encoded. then we can see in the attached test, deparam will change 'ab+ba' to 'ab ba'.

I'm sorry but I don't understand your test case. jQuery does not have a $.deparam method and $.ajax isn't used in the test case although it is supposedly the component being reported. Is this a bug report intended for jQuery core?

The ajax isn't used because I need to setup a server to show it and it's hard to attach the whole server stack. You just need to look at the ajax function of the jQuery code below

if ( s.data && s.processData && typeof s.data !== "string" ) {

s.data = jQuery.param( s.data, s.traditional );

}

there, you don't encode string for ajax calls, but encode string in objects, which is inconsistent

Resetting milestone to future.

If you pass a string to the data option of $.ajax, you are responsible for performing any necessary serialization/encoding of the string. jQuery will not do this for you; if it did, it would end up double-encoding data (or otherwise mangling non-application/x-www-form-urlencoded data).