JSON Data Format

What is JSON

• JSON is a data interchange format. Used to pass data to the web browser, or exchange data with other language, API, or used as a software config file.
• JSON file is plain text file.
• JSON file has file name extension .json.
• JSON format is based on JavaScript objects syntax, of object/array arbitrarily nested.

JSON Code Example

{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 25,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    }
  ],
  "children": [],
  "spouse": null
}

Difference Between JavaScript Syntax vs JSON Syntax

JSON syntax is more strict than JavaScript object/array syntax.

String key must be double quoted

• Good: {"h":2}
• Bad: {h:2}
• Bad: {'h':2}

JSON does not allow extra comma at end.

• good: {"h":2}
• bad: {"h":2,}

JSON does not allow colon at the end.

• good: {"h":2}
• bad: {"h":2};

JSON value does not allow undefined. (but null is ok)

• good: {"h":null}
• bad: {"h":undefined}