Given a valid JSON file containing string like:

[
    {
        "a": 2,
        "b": "test",
        "c": [
            "123"
        ],
        "d": null
    },
    {
        "a": 2,
        "b": "test",
        "c": [
            "123"
        ],
        "d": null
    }
]

and I just want to parse first level and leave lower level as string. So I want the response to be an array like:

Array [
  '{"a":2,"b":"test","c":["123"],"d":null}',
  '{"a":2,"b":"test","c":["123"],"d":null}'
]

where each element is a string.

Actual data I'm trying to parse has dozens of nested levels and several GBs in size and top-level maybe array or object.
Maybe this is string operation problem rather than JSON library problem.