Which Data Type Is Not Supported by JSON?


Larry Thompson

Which Data Type Is Not Supported by JSON?

JSON (JavaScript Object Notation) is a lightweight data interchange format widely used to transmit and store data. It is language-independent and easy for humans to read and write.

However, there are certain data types that JSON does not support. In this article, we will explore these unsupported data types.

1. Date Objects

Date objects are commonly used in programming to represent dates and times.

However, JSON does not have a native way to represent date objects. To work around this limitation, you can convert dates to strings using a standard format such as ISO 8601 before serializing them into JSON.

2. Functions

Functions are executable code blocks that perform specific tasks.

Since JSON is primarily a data format and not a programming language, it does not support the inclusion of functions. If you need to transmit or store code logic, you may consider using other techniques like base64 encoding or transmitting the function as a string.

3. Undefined

The undefined value represents an uninitialized or nonexistent variable in JavaScript.

However, JSON does not have an equivalent data type for undefined values. When serializing data containing undefined values into JSON, these values are typically omitted from the resulting JSON string.

4. NaN and Infinity

NaN (Not-a-Number) and Infinity are special numeric values in JavaScript but cannot be directly represented in JSON. Instead, they will be serialized as null when converted to JSON.


In some programming languages like JavaScript, comments play an essential role in documenting code or adding explanatory notes within scripts.

Sadly, JSON does not support comments natively as it aims to be a concise and efficient data format. Including comments in a JSON file will result in a syntax error.

6. Circular References

A circular reference occurs when an object refers back to itself or creates a cycle with other objects.

JSON does not support circular references due to its nature as a data interchange format. Serializing an object with circular references into JSON will result in an error.


While JSON is a versatile and widely adopted data format, it does have some limitations regarding the types of data it can represent. Understanding these limitations is crucial when working with JSON to ensure proper serialization and deserialization of your data.

In this article, we explored some unsupported data types in JSON, including date objects, functions, undefined values, NaN and Infinity, comments, and circular references. By keeping these limitations in mind, you can effectively work with JSON and make informed decisions when handling complex data structures.

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