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
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | Yes | Yes | 3.5 | 8 | 10.5 | 4 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | 4 | Yes | Yes | Yes |