JSON Duplicate Keys

Douglas Crockford douglas at crockford.com
Thu Jun 6 04:29:03 PDT 2013


The JSON RFC says

     The names within an object SHOULD be unique.

Sadly, there are people in the JavaScript community who interpreted SHOULD to mean DON'T HAVE TO. In a perfect world, we would change the SHOULD to MUST, but we can't. Interoperability and security concerns demand that we specify what happens when keys are duplicated. So we may end up with something like this:

     The names within an object SHOULD be unique. If a key is duplicated,
     a parser SHOULD reject. If it does not reject, it MUST take only the
     last of the duplicated key pairs.

Does anyone see a problem with this?



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