JSON stringify

A common use of JSON is to exchange data to/from a web server.

When sending data to a web server, the data has to be a string.

Convert a JavaScript object into a string with JSON.stringify().

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Stringify a JavaScript Object

Imagine we have this object in JavaScript:

var obj = { "name":"John", "age":30, "city":"New York"};

Use the JavaScript function JSON.stringify() to convert it into a string.

var myJSON = JSON.stringify(obj);

The result will be a string following the JSON notation.

myJSON is now a string, and ready to be sent to a server:

Example

var obj = { "name":"John", "age":30, "city":"New York"};
var myJSON = JSON.stringify(obj);
document.getElementById("demo").innerHTML = myJSON;

You will learn how to send JSON to the server in the next chapter.

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Stringify a JavaScript Array

It is also possible to stringify JavaScript arrays:
Imagine we have this array in JavaScript:

var arr = [ "John", "Peter", "Sally", "Jane" ];

Use the JavaScript function JSON.stringify() to convert it into a string.

var myJSON = JSON.stringify(arr);

The result will be a string following the JSON notation.

myJSON is now a string, and ready to be sent to a server:

Example

var arr = [ "John", "Peter", "Sally", "Jane" ];
var myJSON = JSON.stringify(arr);
document.getElementById("demo").innerHTML = myJSON;

You will learn how to send JSON to the server in the next chapter.

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Exceptions

Stringify Dates

In JSON, date objects are not allowed. The JSON.stringify() function will convert any dates into strings.

Example

var obj = { "name":"John", "today":new Date(), "city":"New York"};
var myJSON = JSON.stringify(obj);

document.getElementById("demo").innerHTML = myJSON;

You can convert the string back into a date object at the receiver.

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Stringify Functions

In JSON, functions are not allowed as object values.
The JSON.stringify() function will remove any functions from a JavaScript object, both the key and the value:

Example

var obj = { "name":"John", "age":function () {return 30;}, "city":"New York"};
var myJSON = JSON.stringify(obj);

document.getElementById("demo").innerHTML = myJSON;

This can be omitted if you convert your functions into strings before running the JSON.stringify() function.

Example

var obj = { "name":"John", "age":function () {return 30;}, "city":"New York"};
obj.age = obj.age.toString();
var myJSON = JSON.stringify(obj);

document.getElementById("demo").innerHTML = myJSON;

You should avoid using functions in JSON, the functions will lose their scope, and you would have to use eval() to convert them back into functions.

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Browser Support

The JSON.stringify() function is included in all major browsers and in the latest ECMAScript (JavaScript) standard:

Web Browsers Support
Firefox 3.5 Internet Explorer 8 Chrome Opera 10 Safari 4

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