How to Comment in JSON Files?

JSON (JavaScript Object Notation) is a lightweight data-interchange format that is easy for humans to read and write and easy for machines to parse and generate. However, JSON does not have a built-in syntax for comments. This limitation can be challenging when you want to annotate your JSON data with explanations or notes for future reference. Despite this, there are several workarounds that developers use to include comments in JSON files.

These are the following approaches:

Using an External Tool or Preprocessor

One method to handle comments in JSON is to use an external tool or preprocessor that strips out comments before the JSON is parsed. This approach allows you to write comments in your JSON file similarly to how you would in JavaScript.

Example: Consider a JSON file with comments (using // for single-line comments).

const data={
    // This is a comment
    "name": "John Doe",
    // The user's age
    "age": 30,
    // The user's email
    "email": "john.doe@example.com"
}

console.log(data)

{ name: 'John Doe', age: 30, email: 'john.doe@example.com' }

Including Comments as Data

Another common approach is to include comments as part of the JSON data itself. This method involves adding comment fields to your JSON objects. This way, the comments are treated as regular key-value pairs.

Example: Here, _comment keys are added to the JSON object and nested objects to provide comments. This method ensures that the JSON remains valid and can be parsed by any JSON parser.

const data={
    "_comment": "This JSON file contains user data",
    "name": "John Doe",
    "age": 30,
    "email": "john.doe@example.com",
    "address": {
        "_comment": "Address details",
        "street": "123 Main St",
        "city": "Anytown"
    }
}
console.log(data)