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Adds the method .serializeJSON() to jQuery (or Zepto) that serializes a form into a JavaScript Object, using the same format as the default Ruby on Rails request params.


Install with bower bower install jquery.serializeJSON, or npm npm install jquery-serializejson, or just download the jquery.serializejson.js script.

And make sure it is included after jQuery, for example:

<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="jquery.serializejson.js"></script>

Usage Example

HTML form:

  <input type="text" name="title" value="Dune"/>
  <input type="text" name="author[name]" value="Frank Herbert"/>
  <input type="text" name="author[period]" value="1945–1986"/>



// returns =>
  title: "Dune",
  author: {
    name: "Frank Herbert",
    period: "1945–1986"

Form input, textarea and select tags are supported. Nested attributes and arrays can be specified by using the attr[nested][nested] syntax.

HTML form:

<form id="my-profile">
  <!-- simple attribute -->
  <input type="text" name="name" value="Mario" />

  <!-- nested attributes -->
  <input type="text" name="address[city]"         value="San Francisco" />
  <input type="text" name="address[state][name]"  value="California" />
  <input type="text" name="address[state][abbr]"  value="CA" />

  <!-- array -->
  <input type="text" name="jobbies[]"             value="code" />
  <input type="text" name="jobbies[]"             value="climbing" />

  <!-- nested arrays, textareas, checkboxes ... -->
  <textarea              name="projects[0][name]">serializeJSON</textarea>
  <textarea              name="projects[0][language]">javascript</textarea>
  <input type="hidden"   name="projects[0][popular]" value="0" />
  <input type="checkbox" name="projects[0][popular]" value="1" checked />

  <textarea              name="projects[1][name]">tinytest.js</textarea>
  <textarea              name="projects[1][language]">javascript</textarea>
  <input type="hidden"   name="projects[1][popular]" value="0" />
  <input type="checkbox" name="projects[1][popular]" value="1"/>

  <!-- select -->
  <select name="selectOne">
    <option value="paper">Paper</option>
    <option value="rock" selected>Rock</option>
    <option value="scissors">Scissors</option>

  <!-- select multiple options, just name it as an array[] -->
  <select multiple name="selectMultiple[]">
    <option value="red"  selected>Red</option>
    <option value="blue" selected>Blue</option>
    <option value="yellow">Yellow</option>



// returns =>
  fullName: "Mario",

  address: {
    city: "San Francisco",
    state: {
      name: "California",
      abbr: "CA"

  jobbies: ["code", "climbing"],

  projects: {
    '0': { name: "serializeJSON", language: "javascript", popular: "1" },
    '1': { name: "tinytest.js",   language: "javascript", popular: "0" }

  selectOne: "rock",
  selectMultiple: ["red", "blue"]

The serializeJSON function returns a JavaScript object, not a JSON String. The plugin should probably have been called serializeObject or similar, but those plugins already existed.

To convert into a JSON String, use the JSON.stringify method, that is available on all major new browsers. If you need to support very old browsers, just include the json2.js polyfill (as described on stackoverfow).

var obj = $('form').serializeJSON();
var jsonString = JSON.stringify(obj);

The plugin implememtation relies on jQuery's .serializeArray() method. This means that it only serializes the inputs supported by .serializeArray(), which follows the standard W3C rules for successful controls. In particular, the included elements cannot be disabled and must contain a name attribute. No submit button value is serialized since the form was not submitted using a button. And data from file select elements is not serialized.

Parse values with :types

Fields values are :string by default. But can be parsed with types by appending a :type suffix to the field name:

  <input type="text" name="default"          value=":string is default"/>
  <input type="text" name="text:string"      value="some text string"/>
  <input type="text" name="excluded:skip"    value="ignored field because of type :skip"/>

  <input type="text" name="numbers[1]:number"        value="1"/>
  <input type="text" name="numbers[1.1]:number"      value="1.1"/>
  <input type="text" name="numbers[other]:number"    value="other"/>

  <input type="text" name="bools[true]:boolean"      value="true"/>
  <input type="text" name="bools[false]:boolean"     value="false"/>
  <input type="text" name="bools[0]:boolean"         value="0"/>

  <input type="text" name="nulls[null]:null"         value="null"/>
  <input type="text" name="nulls[other]:null"        value="other"/>

  <input type="text" name="arrays[empty]:array"         value="[]"/>
  <input type="text" name="arrays[list]:array"          value="[1, 2, 3]"/>

  <input type="text" name="objects[empty]:object"       value="{}"/>
  <input type="text" name="objects[dict]:object"        value='{"my": "stuff"}'/>

// returns =>
  "default": ":string is the default",
  "text": "some text string",
  // excluded:skip is ignored in the output

  "numbers": {
    "1": 1,
    "1.1": 1.1,
    "other": NaN, // <-- "other" is parsed as NaN
  "bools": {
    "true": true,
    "false": false,
    "0": false, // <-- "false", "null", "undefined", "", "0" are parsed as false
  "nulls": {
    "null": null, // <-- "false", "null", "undefined", "", "0"  are parsed as null
    "other": "other" // <-- if not null, the type is a string
  "arrays": { // <-- uses JSON.parse
    "empty": [],
    "not empty": [1,2,3]
  "objects": { // <-- uses JSON.parse
    "empty": {},
    "not empty": {"my": "stuff"}

Types can also be specified with the attribute data-value-type, instead of adding the :type suffix in the field name:

  <input type="text" name="anumb"   data-value-type="number"  value="1"/>
  <input type="text" name="abool"   data-value-type="boolean" value="true"/>
  <input type="text" name="anull"   data-value-type="null"    value="null"/>
  <input type="text" name="anarray" data-value-type="array"   value="[1, 2, 3]"/>

If your field names contain colons (e.g. name="article[my::key][active]") the last part after the colon will be confused as an invalid type. One way to avoid that is to explicitly append the type :string (e.g. name="article[my::key][active]:string"), or to use the attribute data-value-type="string". Data attributes have precedence over :type name suffixes. It is also possible to disable parsing :type suffixes with the option {disableColonTypes: true}.

Custom Types

Use the customTypes option to provide your own type functions. For example:

  <input type="text" name="scary:alwaysBoo" value="not boo"/>
  <input type="text" name="str:string"      value="str"/>
  <input type="text" name="five:number"     value="5"/>
  customTypes: {
    alwaysBoo: (str) => { return "boo"; },

// returns =>
  "scary": "boo",  // <-- parsed with custom type "alwaysBoo"
  "str": "str",    // <-- parsed with default type "string"
  "five": 5,       // <-- parsed with default type "number"

The customTypes option can also include one of the detaultTypes, in which case it will override the default type:

  customTypes: {
    alwaysBoo: (str) => { return "boo"; },
    string: (str) => { return str + "-OVERDRIVE"; },

// returns =>
  "scary": "boo",         // <-- parsed with custom type "alwaysBoo"
  "str": "str-OVERDRIVE", // <-- parsed with custom override "string"
  "five": 5,              // <-- parsed with default type "number"

The default types are defined in $.serializeJSON.defaultOptions.defaultTypes.


With no options, .serializeJSON() returns the same as a regular HTML form submission when serialized as Rack/Rails params. In particular:

  • Values are strings (unless appending a :type to the input name)
  • Unchecked checkboxes are ignored (as defined in the W3C rules for successful controls).
  • Disabled elements are ignored (W3C rules)
  • Keys (input names) are always strings (nested params are objects by default)

Available options:

  • checkboxUncheckedValue: string, return this value on checkboxes that are not checked. Without this option, they would be ignored. For example: {checkboxUncheckedValue: ""} returns an empty string. If the field has a :type, the returned value will be properly parsed; for example if the field type is :boolean, it returns false instead of an empty string.
  • useIntKeysAsArrayIndex: true, when using integers as keys (i.e. <input name="foods[0]" value="banana">), serialize as an array ({"foods": ["banana"]}) instead of an object ({"foods": {"0": "banana"}).
  • skipFalsyValuesForFields: [], skip given fields (by name) with falsy values. You can use data-skip-falsy="true" input attribute as well. Falsy values are determined after converting to a given type, note that "0" as :string (default) is still truthy, but 0 as :number is falsy.
  • skipFalsyValuesForTypes: [], skip given fields (by :type) with falsy values (i.e. skipFalsyValuesForTypes: ["string", "number"] would skip "" for :string fields, and 0 for :number fields).
  • customTypes: {}, define your own :type functions. Defined as an object like { type: function(value){...} }. For example: {customTypes: {nullable: function(str){ return str || null; }}. Custom types extend defaultTypes.
  • defaultTypes: {defaults}, contains the orignal type functions string, number, boolean, null, array, object and skip.
  • defaultType: "string", fields that have no :type suffix and no data-value-type attribute are parsed with the string type function by default, but it could be changed to use a different type function instead.
  • disableColonTypes: true, do not parse input names as types, allowing field names to use colons. If this option is used, types can still be specified with the data-value-type attribute. For example <input name="foo::bar" value="1" data-value-type="number"> will be parsed as a number.

More details about these options in the sections below.

Include unchecked checkboxes

One of the most confusing details when serializing a form is the input type checkbox, because it includes the value if checked, but nothing if unchecked.

To deal with this, a common practice in HTML forms is to use hidden fields for the "unchecked" values:

<!-- Only one booleanAttr will be serialized, being "true" or "false" depending if the checkbox is selected or not -->
<input type="hidden"   name="booleanAttr" value="false" />
<input type="checkbox" name="booleanAttr" value="true" />

This solution is somehow verbose, but ensures progressive enhancement, it works even when JavaScript is disabled.

But, to make things easier, serializeJSON includes the option checkboxUncheckedValue and the possibility to add the attribute data-unchecked-value to the checkboxes:

  <input type="checkbox" name="check1" value="true" checked/>
  <input type="checkbox" name="check2" value="true"/>
  <input type="checkbox" name="check3" value="true"/>

Serializes like this by default:


// returns =>
{check1: 'true'} // check2 and check3 are ignored

To include all checkboxes, use the checkboxUncheckedValue option:

$('form').serializeJSON({checkboxUncheckedValue: "false"});

// returns =>
{check1: "true", check2: "false", check3: "false"}

The data-unchecked-value HTML attribute can be used to targed specific values per field:

<form id="checkboxes">
  <input type="checkbox" name="checked[b]:boolean"   value="true" data-unchecked-value="false" checked/>
  <input type="checkbox" name="checked[numb]"        value="1"    data-unchecked-value="0"     checked/>
  <input type="checkbox" name="checked[cool]"        value="YUP"                               checked/>

  <input type="checkbox" name="unchecked[b]:boolean" value="true" data-unchecked-value="false" />
  <input type="checkbox" name="unchecked[numb]"      value="1"    data-unchecked-value="0" />
  <input type="checkbox" name="unchecked[cool]"      value="YUP" /> <!-- No unchecked value specified -->
$('form#checkboxes').serializeJSON(); // No option is needed if the data attribute is used

// returns =>
  'checked': {
    'b':     true,
    'numb':  '1',
    'cool':  'YUP'
  'unchecked': {
    'bool': false,
    'bin':  '0'
    // 'cool' is not included, because it doesn't use data-unchecked-value

You can use both the option checkboxUncheckedValue and the attribute data-unchecked-value at the same time, in which case the option is used as default value (the data attribute has precedence).

$('form#checkboxes').serializeJSON({checkboxUncheckedValue: 'NOPE'});

// returns =>
  'checked': {
    'b':     true,
    'numb':  '1',
    'cool':  'YUP'
  'unchecked': {
    'bool': false,   // value from data-unchecked-value attribute, and parsed with type "boolean"
    'bin':  '0',     // value from data-unchecked-value attribute
    'cool': 'NOPE'   // value from checkboxUncheckedValue option

Ignore Empty Form Fields

You can use the option .serializeJSON(skipFalsyValuesForTypes: ["string"]), which ignores any string field with an empty value (default type is :string, and empty strings are falsy).

Another option, since serializeJSON() is called on a jQuery object, is to just use the proper jQuery selector to skip empty values (see Issue #28 for more info):

// Select only imputs that have a non-empty value
$('form :input[value!=""]').serializeJSON();

// Or filter them from the form
obj = $('form').find('input').not('[value=""]').serializeJSON();

// For more complicated filtering, you can use a function
obj = $form.find(':input').filter(function () {
          return $.trim(this.value).length > 0

Ignore Fields With Falsy Values

When using :types, you can also skip falsy values (false, "", 0, null, undefined, NaN) by using the option skipFalsyValuesForFields: ["fullName", "address[city]"] or skipFalsyValuesForTypes: ["string", "null"].

Or setting a data attribute data-skip-falsy="true" on the inputs that should be ignored. Note that data-skip-falsy is aware of field :types, so it knows how to skip a non-empty input like this <input name="foo" value="0" data-value-type="number" data-skip-falsy="true"> (Note that "0" as a string is not falsy, but 0 as number is falsy)).

Use integer keys as array indexes

By default, all serialized keys are strings, this includes keys that look like numbers like this:

  <input type="text" name="arr[0]" value="foo"/>
  <input type="text" name="arr[1]" value="var"/>
  <input type="text" name="arr[5]" value="inn"/>

// arr is an object =>
{'arr': {'0': 'foo', '1': 'var', '5': 'inn' }}

Which is how Rack parse_nested_query behaves. Remember that serializeJSON input name format is fully compatible with Rails parameters, that are parsed using this Rack method.

Use the option useIntKeysAsArrayIndex to interpret integers as array indexes:

$('form').serializeJSON({useIntKeysAsArrayIndex: true});

// arr is an array =>
{'arr': ['foo', 'var', undefined, undefined, undefined, 'inn']}

Note: this was the default behavior of serializeJSON before version 2. You can use this option for backwards compatibility.

Option Defaults

All options defaults are defined in $.serializeJSON.defaultOptions. You can just modify it to avoid setting the option on every call to serializeJSON. For example:

$.serializeJSON.defaultOptions.checkboxUncheckedValue = ""; // include unckecked checkboxes as empty strings
$ = (str) => { return str + "-foo"; }; // define global custom type ":foo"


Other plugins solve the same problem in similar ways:

None of them did what I needed at the time serializeJSON was created. Factors that differentiate serializeJSON from the alternatives:

  • Simple and small code base. The minimified version is < 1Kb.
  • Yet flexible enough with features like nested objects, unchecked-checkboxes and custom types.
  • Implemented on top of jQuery (or Zepto) serializeArray, that creates a JavaScript array of objects, ready to be encoded as a JSON string. It takes into account the W3C rules for successful controls, making serializeJSON as standard and stable as it can be.
  • The format for the input field names is the same used by Rails (from Rack::Utils.parse_nested_query), that is successfully used by many backend systems and already well understood by many front end developers.
  • Exaustive test suite helps iterate on new releases and bugfixes with confidence.
  • Compatible with bower, zepto.js and pretty much every version of jQuery.


Contributions are awesome. Feature branch pull requests are the preferred method. Just make sure to add tests for it. To run the jasmine specs, just open spec/spec_runner_jquery.html in your browser.


  • 3.1.0 (Sep 13, 2020): Rename option disableColonTypes that was mistakenly named disableSemicolonTypes. Fix typos in README.
  • 3.0.0 (Sep 06, 2020): Improve types (PR #105) and remove parsing options (PR #104). The type system with :type suffixes, data-value-type attributes, and a combination of the options customTypes, disableColonTypes and defaultType, are safer and easier to use than the previous options parseNumbers, parseAll, etc. Thanks Laykou for suggesting [PR #102] that pointed the problems of inputs with colons in their names.
  • 2.9.0 (Jan 12, 2018): Overrides to customTypes.string function now also apply to fields with no type, because :string is the default implicit type. Thanks JocaPC for reporting the issue #83.
  • 2.8.1 (Dec 09, 2016): Identify issue #67 and throw a descriptive error with a link to the issue, that explains why nested arrays of objects with checkboxes with unchecked values are not supported.
  • 2.8.0 (Dec 09, 2016): Add options skipFalsyValuesForFields, skipFalsyValuesForTypes and attr data-skip-falsy to easily skip falsy values (which includes empty strings). Thanks to milkaknap.
  • 2.7.2 (Dec 19, 2015): Bugfix #55 (Allow data types with the data-value-type attribute to use brackets in names). Thanks to stricte.
  • 2.7.1 (Dec 12, 2015): Bugfix #54 (data-value-type attribute only works with input elements). Thanks to madrabaz.
  • 2.7.0 (Nov 28, 2015): Allow to define custom types with the data-value-type attribute. Thanks to madrabaz.
  • 2.6.2 (Oct 24, 2015): Add support for AMD/CommonJS/Browserify modules. Thanks to jisaacks.
  • 2.6.1 (May 13, 2015): Bugfix #43 (Fix IE 8 compatibility). Thanks to rywall.
  • 2.6.0 (Apr 24, 2015): Allow to define custom types with the option customTypes and inspect/override default types with the option defaultTypes. Thanks to tygriffin for the pull request.
  • 2.5.0 (Mar 11, 2015): Override serialized properties if using the same name, even for nested values, instead of crashing the script, fixing issue#29. Also fix a crash when using Zepto and the data-unchecked-value option.
  • 2.4.2 (Feb 04, 2015): Ignore disabled checkboxes with "data-unchecked-value". Thanks to skarr for the pull request.
  • 2.4.1 (Oct 12, 2014): Add :auto type, that works like the parseAll option, but targeted to a single input.
  • 2.4.0 (Oct 12, 2014): Implement :types. Types allow to easily specify how to parse each input.
  • 2.3.2 (Oct 11, 2014): Bugfix #27 (parsing error on nested keys like name="foo[inn[bar]]"). Thanks to danlo for finding the issue.
  • 2.3.1 (Oct 06, 2014): Bugfix #22 (ignore checkboxes with no name when doing checkboxUncheckedValue). Thanks to KATT for finding and fixing the issue.
  • 2.3.0 (Sep 25, 2014): Properly spell "data-unckecked-value", change for "data-unchecked-value"
  • 2.2.0 (Sep 17, 2014): Add option checkboxUncheckedValue and attribute data-unckecked-value to allow parsing unchecked checkboxes.
  • 2.1.0 (Jun 08, 2014): Add option parseWithFunction to allow custom parsers. And fix issue #14: empty strings were parsed as a zero when parseNumbers option was true.
  • 2.0.0 (May 04, 2014): Nested keys are always object attributes by default (discussed on issue #12). Set option $.serializeJSON.defaultOptions.useIntKeysAsArrayIndex = true; for backwards compatibility (see Options section). Thanks to joshuajabbour for finding the issue.
  • 1.3.0 (May 03, 2014): Accept options {parseBooleans, parseNumbers, parseNulls, parseAll} to modify what type to values are interpreted from the strings. Thanks to diaswrd for finding the issue.
  • 1.2.3 (Apr 12, 2014): Lowercase filenames.
  • 1.2.2 (Apr 03, 2014): Now also works with Zepto.js.
  • 1.2.1 (Mar 17, 2014): Refactor, cleanup, lint code and improve test coverage.
  • 1.2.0 (Mar 11, 2014): Arrays with empty index and objects with empty values are added and not overriden. Thanks to kotas.
  • 1.1.1 (Feb 16, 2014): Only unsigned integers are used to create arrays. Alphanumeric keys are always for objects. Thanks to Nicocin.
  • 1.0.2 (Jan 07, 2014): Tag to be on the jQuery plugin registry.
  • 1.0.1 (Aug 20, 2012): Bugfix: ensure that generated arrays are being displayed when parsed with JSON.stringify
  • 1.0.0 (Aug 20, 2012): Initial release


Written and maintained by Mario Izquierdo

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