Customization Options Across Popular JSON Formatters

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. While the format itself is standardized, how it is *formatted* can vary significantly. JSON formatters are tools or libraries that take raw JSON data and output it in a structured, often more readable, form. Understanding the customization options they offer is crucial for developers dealing with data readability, standardization, debugging, and integration.

Whether you're using built-in language functions like JavaScript's JSON.stringify(), command-line tools like jq, or popular code formatters like Prettier, these tools provide options to control the output. This page explores some of the most common and useful customization options you'll encounter.

Why Customize JSON Output?

Customizing JSON output serves several purposes:

• Readability: Pretty-printing with indentation makes nested structures easier to follow.
• Standardization: Ensuring consistent formatting across a project or team simplifies code reviews and debugging.
• Debugging: Formatting can highlight structural issues or unexpected data within the JSON.
• Data Processing: Filtering keys or handling specific data types (like BigInts or dates) can be necessary before data consumption or transfer.
• Minification: Producing compact JSON without whitespace reduces file size for network transfer or storage.

Indentation & Whitespace

This is perhaps the most common customization. JSON is often transferred in a compact, whitespace-free form to save bandwidth. However, this makes it difficult for humans to read. Formatters can "pretty-print" JSON by adding indentation and newlines.

• Enable/Disable Pretty-Printing: The most basic option is turning pretty-printing on or off.
• Indent Style (Spaces vs. Tabs): Choose between using space characters or tab characters for indentation.
• Indent Size: Specify the number of spaces per indentation level (commonly 2 or 4) or the width of a tab character.

{"name":"Example Object","version":1.5,"isActive":true,"tags":["data","json","formatting"],"details":{"id":"abc-123","created":"2023-10-27T10:00:00Z","lastUpdated":null,"value":"12345678901234567890","config":{"optionA":true,"optionB":false}},"count":42}

{
  "name": "Example Object",
  "version": 1.5,
  "isActive": true,
  "tags": [
    "data",
    "json",
    "formatting"
  ],
  "details": {
    "id": "abc-123",
    "created": "2023-10-27T10:00:00Z",
    "lastUpdated": null,
    "value": "12345678901234567890",
    "config": {
      "optionA": true,
      "optionB": false
    }
  },
  "count": 42
}

{
    "name": "Example Object",
    "version": 1.5,
    "isActive": true,
    "tags": [
        "data",
        "json",
        "formatting"
    ],
    "details": {
        "id": "abc-123",
        "created": "2023-10-27T10:00:00Z",
        "lastUpdated": null,
        "value": "12345678901234567890",
        "config": {
            "optionA": true,
            "optionB": false
        }
    },
    "count": 42
}

Key Sorting

By default, the order of keys within a JSON object is not guaranteed or standardized. However, for purposes like generating consistent diffs between JSON files, improving readability by grouping related keys, or ensuring deterministic output, sorting keys alphabetically is a common requirement.

Many formatters provide an option to sort keys either alphabetically or sometimes based on a custom comparison function. Note that JSON.stringify in JavaScript does not natively support sorting keys. Libraries or custom replacer functions are needed for this.

{
  "name": "Example Object",
  "version": 1.5,
  "isActive": true,
  "tags": [
    "data",
    "json",
    "formatting"
  ],
  "details": {
    "id": "abc-123",
    "created": "2023-10-27T10:00:00Z",
    "lastUpdated": null,
    "value": "12345678901234567890",
    "config": {
      "optionA": true,
      "optionB": false
    }
  },
  "count": 42
}

{
  "count": 42,
  "details": {
    "config": {
      "optionA": true,
      "optionB": false
    },
    "created": "2023-10-27T10:00:00Z",
    "id": "abc-123",
    "lastUpdated": null,
    "value": "12345678901234567890"
  },
  "isActive": true,
  "name": "Example Object",
  "tags": [
    "data",
    "json",
    "formatting"
  ],
  "version": 1.5
}

Filtering & Transformation (Replacer)

Beyond just structural formatting, many tools allow you to control which data makes it into the final JSON output or how certain data types are represented.

• Excluding Keys/Values: Remove specific keys, or remove keys whose values are null, undefined, empty strings, etc.
• Handling Special Data Types: Convert types like BigInt, Date objects, or other custom objects into standard JSON types (string, number, boolean, object, array, null).
• Mapping/Transforming Values: Modify values before they are serialized (e.g., rounding numbers, formatting dates).

In JavaScript, the second argument of JSON.stringify is a "replacer" function or array that allows for powerful filtering and transformation.

{
  "name": "Example Object",
  "version": 1.5,
  "isActive": true,
  "tags": [
    "data",
    "json",
    "formatting"
  ],
  "details": {
    "id": "abc-123",
    "created": "2023-10-27T10:00:00Z",
    "lastUpdated": null,
    "value": "12345678901234567890",
    "config": {
      "optionA": true,
      "optionB": false
    }
  },
  "count": 42
}

{
  "name": "Example Object",
  "version": 1.5,
  "isActive": true,
  "tags": [
    "data",
    "json",
    "formatting"
  ],
  "details": {
    "id": "abc-123",
    "created": "2023-10-27T10:00:00Z",
    "value": "12345678901234567890",
    "config": {
      "optionA": true,
      "optionB": false
    }
  }
}

Key Quoting

According to the JSON standard, object keys must always be strings enclosed in double quotes. However, some non-standard variants or tools might allow unquoted keys for simple identifiers (like in JavaScript object literals). Standard JSON formatters strictly adhere to quoting keys. Some tools might offer options related to this, though it's less common for strict JSON output.

More relevant might be options around when to quote string values if they are allowed to be unquoted in certain contexts (not standard JSON). For standard JSON, all keys and string values are always quoted.

{
  "standardKey": "value",
  "another-key": 123
}

Handling Empty Structures or Specific Values

Some formatters provide explicit options for handling specific scenarios:

• Empty Objects/Arrays: How empty or [] are formatted (e.g., on a single line or with newlines).
• Null/Undefined Handling: Explicit options to drop keys with null or undefined values (as shown with the replacer, but sometimes a simple flag).
• Maximum Depth: Limit the depth of nested objects/arrays to prevent infinite recursion or overly large output for deep structures.

Conclusion

The customization options offered by JSON formatters are powerful tools for developers. From improving human readability through indentation and sorting to controlling the data payload via filtering and type transformation, these options ensure JSON is not just a data format but one that can be tailored to specific use cases and environments. Understanding how to leverage options like indentation, key sorting, and replacer functions (like in JSON.stringify) or flags in command-line tools allows for more efficient development, debugging, and data management workflows.