JSON.stringify()

JSON is often used to exchange data with the server.

When sending data to the server, it is generally a string.

We can use the JSON.stringify() method to convert a JavaScript object to a string.

Syntax

JSON.stringify(value[, replacer[, space]])

Parameter description:

  • value:

    Required. The JavaScript value to convert (usually an object or array).

  • replacer:

    Optional. A function or array used to transform the result.

    If replacer is a function, JSON.stringify will call that function, passing in the key and value of each member. The return value is used instead of the original value. If this function returns undefined, the member is excluded. The key for the root object is an empty string: "".

    If replacer is an array, only members with key values present in the array are converted. The conversion order of members is the same as the order of keys in the array. When the value parameter is also an array, the replacer array is ignored.

  • space:

    Optional. Adds indentation, spaces, and line breaks to the text. If space is a number, the return value text is indented by the specified number of spaces at each level. If space is greater than 10, the text is indented 10 spaces. space can also be a non-number, such as \t.

JavaScript Object Conversion

For example, we send the following data to the server:

var obj = { "name":"example", "alexa":10000, "site":"www.example.com"};

We use the JSON.stringify() method to process the above data and convert it to a string:

var myJSON = JSON.stringify(obj);

myJSON is a string.

We can send myJSON to the server:

Example

var obj = { "name":"example", "alexa":10000, "site":"www.example.com"}; var myJSON = JSON.stringify(obj); document.getElementById("demo").innerHTML = myJSON;

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JavaScript Array Conversion

We can also convert a JavaScript array into a JSON string:

Example

var arr = [ "Google", "Example", "Taobao", "Facebook" ]; var myJSON = JSON.stringify(arr);

myJSON is a string.

We can send myJSON to the server:

Example

var arr = [ "Google", "Example", "Taobao", "Facebook" ]; var myJSON = JSON.stringify(arr); document.getElementById("demo").innerHTML = myJSON;

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Exceptions

Parsing Data

JSON cannot store Date objects.

JSON.stringify() will convert all dates to strings.

Example

var obj = { "name":"Example", "initDate":new Date(), "site":"www.example.com"}; var myJSON = JSON.stringify(obj); document.getElementById("demo").innerHTML = myJSON;

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After that, you can convert the string back into a Date object.

Parsing Functions

JSON does not allow functions. JSON.stringify() will remove functions from JavaScript objects, including the key and value.

Example

var obj = { "name":"Example", "alexa":function () {return 10000;}, "site":"www.example.com"}; var myJSON = JSON.stringify(obj); document.getElementById("demo").innerHTML = myJSON;

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We can avoid the above problem by converting the function to a string before executing the JSON.stringify() function:

Example

var obj = { "name":"Example", "alexa":function () {return 10000;}, "site":"www.example.com"}; obj.alexa = obj.alexa.toString(); var myJSON = JSON.stringify(obj); document.getElementById("demo").innerHTML = myJSON;

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It is not recommended to use functions in JSON.

Browser Support

Mainstream browsers all support the JSON.stringify() function:

  • Firefox 3.5
  • Internet Explorer 8
  • Chrome
  • Opera 10
  • Safari 4
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