JSON string parser without literals

Question

How to check if a string like this {:[{},{}]}, without any literals, can be represented as a JSON object or not?

The input comes with the following constraints: 1. A JSON object should start with '{' and ends with a '}'. 2. The key and value should be separated by a ':'. 3. A ',' suggests an additional JSON property. 4. An array only consists of JSON objects. It cannot contain a "key":"value" pair by itself.

And it is to be intrepreted like this:

{
"Key": [{
"Key": "Value"
}, {
"Key": "Value"
}]
}

Do you mean you want to check if your string is valid JSON (that would parse to an object)? — Thilo
– Thilo, Commented Aug 20, 2016 at 6:13
I meant without anything like 'key', 'value, 'abc', '123' etc. — user4032054
– user4032054, Commented Aug 20, 2016 at 6:14
Possible duplicate of How do I check if a string is valid JSON in Python? — Ahasanul Haque
– Ahasanul Haque, Commented Aug 20, 2016 at 6:21
What is "the wrong answer"? For the record, it is not valid JSON. See the railroad diagrams here: json.org — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Aug 20, 2016 at 6:21

S McCrohan · Accepted Answer · 2016-08-20 06:37:56Z

1

The syntax spec for JSON can be found here.

It indicates that the [{},{}] is legal, because [] has to contain 0 or more elements separated by ,, and {} is a legal element. However, the first part of your example is NOT valid - the : must have a string in front of it. While it is legal for it to be an empty string, it's not legal for it to be null, and the interpretation of a totally missing element is ambiguous.

So. {"":[{},{}]} is legal, but {:[{},{}]} is not.

answered Aug 20, 2016 at 6:37

S McCrohan

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