JavaScript JSON parse() Method

Definition and Usage

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

The string must be written in JSON format.

The JSON.parse() method can choose to use a function to convert the result.

Instance

Example 1

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

var obj = JSON.parse('{"firstName":"Bill", "lastName":"Gates"}');

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Example 2

How to use the reviver function:

/* Replace the "city" value with uppercase: */
var text = '{ "name":"Bill", "age":"19", "city":"Seattle"}';
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;

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Example 3

Parse 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

Please see json_demo.txt

Syntax

JSON.parse(string, function)

Parameter value

Parameter Description
string Required. A string written in JSON format.
reviver function

Optional. A function used to transform the result. This function is called for each item. Any nested objects are transformed before the parent object.

If this function returns a valid value, then replace the item value with the converted value.

If this function returns undefined, then remove this item.

Technical details

Return value: JSON object, or number.
JavaScript version: ECMAScript 5

Browser support

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

Method Chrome IE Firefox Safari Opera
parse() 4.0 8.0 3.5 4.0 11.5

Related Pages

JSON Tutorial:Introduction to JSON