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JavaScript Handbook

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JSON Data Types in JavaScript

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JSON Data Types

JSON (JavaScript Object Notation) supports a limited set of data types. Unlike JavaScript, it cannot directly store functions, dates, or undefined values.

  • JSON is text-based; all data is transmitted as strings.
  • JSON is language-independent, but its syntax comes from JavaScript.
  • Use JSON.parse() to convert JSON strings into JavaScript objects.
  • Use JSON.stringify() to convert JavaScript objects into JSON strings.

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1. String

  • A sequence of characters enclosed in double quotes ("").
  • Strings must use double quotes in JSON; single quotes are invalid.
  • Example:
"name": "John"

2. Number

  • Numeric values: integers or floating-point numbers.
  • No quotes around numbers.
  • Examples:
"age": 30
"price": 19.99

3. Object

  • An unordered collection of key/value pairs.
  • Enclosed in curly braces {}.
  • Keys must be strings (double quotes), values can be any JSON type.
  • Example:
"address": {
  "street": "123 Main St",
  "city": "New York",
  "zip": 10001
}

4. Array

  • An ordered list of values, enclosed in square brackets [].
  • Values can be of any JSON type, including objects or arrays.
  • Example:
"employees": [
  {"firstName": "John", "lastName": "Doe"},
  {"firstName": "Anna", "lastName": "Smith"},
  {"firstName": "Peter", "lastName": "Jones"}
]

5. Boolean

  • Represents logical values: true or false (no quotes).
  • Example:
"isActive": true"isAdmin": false

6. Null

  • Represents an empty or unknown value.
  • Always written as null (no quotes).
  • Example:
"middleName": null

 

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