Detect and reject trailing commas

[richfitz]

They are not valid JSON and so should not be permitted. jsonlite doesn't care, and nor does passing them directly through to V8

[aismaniotto]

Can you let a little bit more clear? Has some example?

[richfitz]

Trailing commas in arrays or objects are valid JavaScript but not valid JSON. For example:

[1, 2, ]

and

{
  "a": 1,
  "b": 2,
}

are not valid json (https://jsonlint.com) but can be passed into jsonvalidate because it never actually parses inputs as json