JSON Formatter & Beautifier

JSON Explained

What is JSON?

JSON stands for JavaScript Object Notation and is pronounced "Jason". It is a human-readable and compact text format used to represent structured data and to exchange it between systems. It is defined by RFC 8259 and ECMA-404.

Why use JSON?

• It is human readable… if it is properly formatted!
• It is compact because it does not use a full markup structure, unlike XML.
• It is easy to parse in every programming language and a huge number of libraries are available.
• The data structure (objects, arrays, values) maps naturally to the types of most languages.

JSON format rules

• Objects are enclosed in curly brackets { }; an empty object is {}.
• Arrays are enclosed in square brackets [ ]; an empty array is [].
• A member is a key-value pair. The key must be a string in double quotes and should be unique within an object.
• String values must be enclosed in double quotes. "Offensive" characters (", \, control characters) must be escaped with a backslash.
• Booleans are the literals true and false, in lower case. Null is the literal null.
• Numbers use double-precision floating point format; scientific notation is supported. Numbers must not have leading zeroes and cannot be NaN or Infinity.
• Dates and other types are not supported natively and should be represented as strings (ISO 8601 is recommended).
• Each member of an object or item of an array must be followed by a comma unless it is the last one (no trailing commas).
• The common extension for JSON files is .json and the MIME type is application/json.

{
   "anObject": {
      "numericProperty": -122,
      "stringProperty": "An offensive \" is problematic",
      "nullProperty": null,
      "booleanProperty": true,
      "dateProperty": "2011-09-23"
   },
   "arrayOfObjects": [ { "item": 1 }, { "item": 2 }, { "item": 3 } ],
   "arrayOfIntegers": [ 1, 2, 3, 4, 5 ]
}

JSON in JavaScript

Never parse JSON with eval(): it executes arbitrary code and opens the door to security issues. Use JSON.parse() instead, and JSON.stringify() to produce JSON:

// A valid json string
const someJsonString = '{"someProperty":"someValue"}';
const jsonObject = JSON.parse(someJsonString);
console.log(jsonObject.someProperty);     // "someValue"

const text = JSON.stringify({ a: 1, b: [1, 2] }, null, 3);   // pretty printed with 3 spaces