var body = ' { name: test, description: test json, website: domain.com } ';

JSON.stringify(JSON.parse(body))

Returns:

{name:test,description:test json,website:domain.com}

Which is exactly what you want. And yes, JSON.stringify with 1 parameter is guaranteed to give the shortest possible JSON, meaning no obsolete whitespace outside keys and values. That's the default because JSON is, in nearly all situations, intended to be a highly efficient recursive data serialization method - unnecessary whitespace has no use there by default.

The full syntax is actually:

JSON.stringify(value[, replacer [, space]])

The optional third parameter defaults to false - if set to another value it produces 'pretty print' with extra whitespace or lead-in strings:

The space argument may be used to control spacing in the final string.
If it is a number, successive levels in the stringification will each
be indented by this many space characters (up to 10). If it is a
string, successive levels will indented by this string (or the first
ten characters of it).

As a final note, you shouldn't even want to use a regexp for this. Regexps are for making sense out of character patterns, not for processing structured data like XML, HTML or JSON. In those cases, use an XML, DOM or JSON parser respectively and process the results in there.