What does it mean when the JSON is marked as invalid due to it being undefined?

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When a JSON is marked as invalid due to it being undefined, it means that the JSON object or value being referred to does not exist or has not been defined. This can happen if a JSON object is expected to have a certain key or property but the key is missing, or if a variable containing JSON data is undefined. This can result in errors or unexpected behavior when trying to work with the JSON data.