Widely available Essential for web development, but best used with explicit validation and clear expectations about the resulting data shape.

JSON

The JSON namespace object contains static methods for parsing values from and converting values to JavaScript Object Notation (JSON).

DataSerializationJSON

Browser support

Feature Desktop Mobile
Chrome
Edge
Firefox
Safari
Chrome Android
Safari iOS
JSON
3
12
3.5
4
18
4
JSON.json superset

JSON is a syntax for serializing objects, arrays, numbers, strings, booleans, and null. It is based upon JavaScript syntax, but is distinct from JavaScript: most of JavaScript is not JSON. For example:
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JSON.parse

The JSON.parse() static method parses a JSON string, constructing the JavaScript value or object described by the string. An optional reviver function can be provided to perform a transformation on the resulting object before it is returned.
3
12
3.5
4
18
4
JSON.stringify

The JSON.stringify() static method converts a JavaScript value to a JSON string, optionally replacing values if a replacer function is specified or optionally including only the specified properties if a replacer array is specified.
3
12
3.5
4
18
4
JSON.stringify.well formed stringify

Strings are escaped to well-formed UTF-8
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12.1
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1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)

Syntax

JAVASCRIPT 
// Parse
const obj = JSON.parse('{\"name\": \"Taro\", \"age\": 25}');

// Convert to string
const json = JSON.stringify(obj);

// Format output
JSON.stringify(obj, null, 2);

// Use `replacer` to output only specific keys
JSON.stringify(obj, ['name']); // '{\"name\":\"Taro\"}'

Live demo

Formatted output with JSON.stringify

Use the third argument (spacing) to format the output in a readable way.

PreviewFullscreen

JSON.parse error handling

Catch the error thrown when invalid JSON is parsed.

PreviewFullscreen

Extract specific keys with replacer

Serialize only the keys passed in the replacer array.

PreviewFullscreen

Use cases

  • API payload handling

    Decode server responses and prepare client data for transport in a well-known text format.

  • Storing structured data

    Serialize lightweight state or exportable records when a plain text representation is useful.

Cautions

  • JSON loses functions, undefined, and some richer object types, so it is not a general-purpose cloning strategy.
  • Parsing untrusted text should be paired with schema or shape validation before the data drives application logic.

Accessibility

  • If parsed data feeds user-facing UI, validate labels and text so broken payloads do not produce confusing or empty interfaces.

Related links