Does JSON syntax allow duplicate keys in an object?

Question

Is this valid json?

{
    \"a\" : \"x\",
    \"a\" : \"y\"
}

http://jsonlint.com/ says yes.

http://www.json.org/ doesn\'t say anyth

Answer 1

It's not defined in the ECMA JSON standard. And generally speaking, a lack of definition in a standard means, "Don't count on this working the same way everywhere."

If you're a gambler, "many" JSON engines will allow duplication and simply use the last-specified value. This:

var o = {"a": 1, "b": 2, "a": 3}

Becomes this:

Object {a: 3, b: 2}

But if you're not a gambler, don't count on it!