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JavaScript JSON parse() Method

❮ JavaScript JSON Object

Example

Parse a string (written in JSON format) and return a JavaScript object:

var obj = JSON.parse('{"firstName":"John", "lastName":"Doe"}');
Try it Yourself »

More "Try it Yourself" examples below.


Definition and Usage

The JSON.parse() method parses a string and returns a JavaScript object.

The string has to be written in JSON format.

The JSON.parse() method can optionally transform the result with a function.


Browser Support

The numbers in the table specify the first browser version that fully supports the method.

Method
parse() 4.0 8.0 3.5 4.0 11.5

Syntax

JSON.parse(string, function)

Parameter Values

Parameter Description
string Required. A string written in JSON format
reviver function Optional. A function used to transform the result. The function is called for each item. Any nested objects are transformed before the parent.
  • If the function returns a valid value, the item value is replaced with the transformed value
  • If the function returns null or undefined, the item is deleted


Technical Details

Return Value: A JSON Object, or Array
JavaScript Version: ECMAScript 5

More Examples

Example

How to use the reviver function:

/*replace the value of "city" to upper case:*/
var text = '{ "name":"John", "age":"39", "city":"New York"}';
var obj = JSON.parse(text, function (key, value) {
  if (key == "city") {
    return value.toUpperCase();
  } else {
    return value;
  }
});

document.getElementById("demo").innerHTML = obj.name + ", " + obj.city;
Try it Yourself »

Example

Parsing JSON received from the server:

var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
  if (this.readyState == 4 && this.status == 200) {
    var myObj = JSON.parse(this.responseText);
    document.getElementById("demo").innerHTML = myObj.name;
  }
};
xmlhttp.open("GET", "json_demo.txt", true);
xmlhttp.send();
Try it Yourself »

Take a look at json_demo.txt


❮ JavaScript JSON Object