The JSON.parse() 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.

Syntax

JSON.parse(text[, reviver])

Parameters

text
The string to parse as JSON. See the JSON object for a description of JSON syntax.
reviver Optional
If a function, this prescribes how the value originally produced by parsing is transformed, before being returned.

Return value

The Object corresponding to the given JSON text.

Exceptions

Throws a SyntaxError exception if the string to parse is not valid JSON.

Examples

Using JSON.parse()

JSON.parse('{}');              // {}
JSON.parse('true');            // true
JSON.parse('"foo"');           // "foo"
JSON.parse('[1, 5, "false"]'); // [1, 5, "false"]
JSON.parse('null');            // null

Using the reviver parameter

If a reviver is specified, the value computed by parsing is transformed before being returned. Specifically, the computed value and all its properties (beginning with the most nested properties and proceeding to the original value itself) are individually run through the reviver. Then it is called, with the object containing the property being processed as this, and with the property name as a string, and the property value as arguments. If the reviver function returns undefined (or returns no value, for example, if execution falls off the end of the function), the property is deleted from the object. Otherwise, the property is redefined to be the return value.

If the reviver only transforms some values and not others, be certain to return all untransformed values as-is, otherwise they will be deleted from the resulting object.

JSON.parse('{"p": 5}', (key, value) =>
  typeof value === 'number'
    ? value * 2 // return value * 2 for numbers
    : value     // return everything else unchanged
);

// { p: 10 }

JSON.parse('{"1": 1, "2": 2, "3": {"4": 4, "5": {"6": 6}}}', (key, value) => {
  console.log(key); // log the current property name, the last is "".
  return value;     // return the unchanged property value.
});

// 1
// 2
// 4
// 6
// 5
// 3 
// ""

JSON.parse() does not allow trailing commas

// both will throw a SyntaxError
JSON.parse('[1, 2, 3, 4, ]');
JSON.parse('{"foo" : 1, }');

Specifications

Specification Status Comment
ECMAScript 5.1 (ECMA-262)
The definition of 'JSON.parse' in that specification.
Standard Initial definition. Implemented in JavaScript 1.7.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'JSON.parse' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'JSON.parse' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes3.5810.54
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes4 Yes Yes Yes

See also