Serializing to JSON in jQuery [duplicate]

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I need to serialize an object to JSON. I'm using jQuery. Is there a "standard" way to do this?

My specific situation: I have an array defined as shown below:

var countries = new Array();
countries[0] = 'ga';
countries[1] = 'cd';

and I need to turn this into a string to pass to $.ajax() like this:

    type: "POST",
    url: "Concessions.aspx/GetConcessions",
    data: "{'countries':['ga','cd']}",

JSON-js - JSON in JavaScript.

To convert an object to a string, use JSON.stringify:

var json_text = JSON.stringify(your_object, null, 2);

To convert a JSON string to object, use JSON.parse:

var your_object = JSON.parse(json_text);

It was recently recommended by John Resig:

...PLEASE start migrating your JSON-using applications over to Crockford's json2.js. It is fully compatible with the ECMAScript 5 specification and gracefully degrades if a native (faster!) implementation exists.

In fact, I just landed a change in jQuery yesterday that utilizes the JSON.parse method if it exists, now that it has been completely specified.

I tend to trust what he says on JavaScript matters :)

All modern browsers (and many older ones which aren't ancient) support the JSON object natively. The current version of Crockford's JSON library will only define JSON.stringify and JSON.parse if they're not already defined, leaving any browser native implementation intact.

I've been using jquery-json for 6 months and it works great. It's very simple to use:

var myObj = {foo: "bar", "baz": "wockaflockafliz"};

// Result: {"foo":"bar","baz":"wockaflockafliz"}

Works on IE8+

No need for jQuery, use:


I haven't used it but you might want to try the jQuery plugin written by Mark Gibson

It adds the two functions: $.toJSON(value), $.parseJSON(json_str, [safe]).

No, the standard way to serialize to JSON is to use an existing JSON serialization library. If you don't wish to do this, then you're going to have to write your own serialization methods.

If you want guidance on how to do this, I'd suggest examining the source of some of the available libraries.

EDIT: I'm not going to come out and say that writing your own serliazation methods is bad, but you must consider that if it's important to your application to use well-formed JSON, then you have to weigh the overhead of "one more dependency" against the possibility that your custom methods may one day encounter a failure case that you hadn't anticipated. Whether that risk is acceptable is your call.

I did find this somewhere. Can't remember where though... probably on StackOverflow :)

$.fn.serializeObject = function(){
    var o = {};
    var a = this.serializeArray();
    $.each(a, function() {
        if (o[]) {
            if (!o[].push) {
                o[] = [o[]];
            o[].push(this.value || '');
        } else {
            o[] = this.value || '';
    return o;

If you don't want to use external libraries there is .toSource() native JavaScript method, but it's not perfectly cross-browser.

The best way is to include the polyfill for JSON object.

But if you insist create a method for serializing an object to JSON notation (valid values for JSON) inside the jQuery namespace, you can do something like this:


// This is a reference to JSON.stringify and provides a polyfill for old browsers.
// stringify serializes an object, array or primitive value and return it as JSON.
jQuery.stringify = (function ($) {
  if (window.JSON && typeof JSON.stringify === "function")
    return JSON.stringify;

  _PRIMITIVE = /string|number|boolean|null/;

  _OPEN = {
    object: "{",
    array: "["

  _CLOSE = {
    object: "}",
    array: "]"

  //actions to execute in each iteration
  function action(key, value) {
    var type = $.type(value),
      prop = "";

    //key is not an array index
    if (typeof key !== "number") {
      prop = '"' + key + '":';
    if (type === "string") {
      prop += '"' + value + '"';
    } else if (_PRIMITIVE.test(type)) {
      prop += value;
    } else if (type === "array" || type === "object") {
      prop += toJson(value, type);
    } else return;

  //iterates over an object or array
  function each(obj, callback, thisArg) {
    for (var key in obj) {
      if (obj instanceof Array) key = +key;, key, obj[key]);

  //generates the json
  function toJson(obj, type) {
    var items = [];
    each(obj, action, items);
    return _OPEN[type] + items.join(",") + _CLOSE[type];

  //exported function that generates the json
  return function stringify(obj) {
    if (!arguments.length) return "";
    var type = $.type(obj);
    if (_PRIMITIVE.test(type))
      return (obj === null ? type : obj.toString());
    //obj is array or object
    return toJson(obj, type);


var myObject = {
    "0": null,
    "total-items": 10,
    "undefined-prop": void(0),
    sorted: true,
    images: ["bg-menu.png", "bg-body.jpg", [1, 2]],
    position: { //nested object literal
        "x": 40,
        "y": 300,
        offset: [{ top: 23 }]
    onChange: function() { return !0 },
    pattern: /^bg-.+\.(?:png|jpe?g)$/i

var json = jQuery.stringify(myObject);

Yes, you should JSON.stringify and JSON.parse your Json_PostData before calling $.ajax:

        url:    post_http_site,  
        type: "POST",         
        data:   JSON.parse(JSON.stringify(Json_PostData)),       
        cache: false,
        error: function (xhr, ajaxOptions, thrownError) {
            alert(" write json item, Ajax error! " + xhr.status + " error =" + thrownError + " xhr.responseText = " + xhr.responseText );    
        success: function (data) {
            alert("write json item, Ajax  OK");


It's basically 2 step process:

First, you need to stringify like this

var JSON_VAR = JSON.stringify(OBJECT_NAME, null, 2); 

After that, you need to convert the string to Object

var obj = JSON.parse(JSON_VAR);

One thing that the above solutions don't take into account is if you have an array of inputs but only one value was supplied.

For instance, if the back end expects an array of People, but in this particular case, you are just dealing with a single person. Then doing:

<input type="hidden" name="People" value="Joe" />

Then with the previous solutions, it would just map to something like:

    "People" : "Joe"

But it should really map to

    "People" : [ "Joe" ]

To fix that, the input should look like:

<input type="hidden" name="People[]" value="Joe" />

And you would use the following function (based off of other solutions, but extended a bit)

$.fn.serializeObject = function() {
var o = {};
var a = this.serializeArray();
$.each(a, function() {
    if ( == "[]"){ =, - 2);
        o[] = [];

    if (o[]) {
        if (!o[].push) {
            o[] = [o[]];
        o[].push(this.value || '');
    } else {
        o[] = this.value || '';
return o;