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>

HTML form:

<form>
  <input type="text" name="title" value="Finding Loot"/>
  <input type="text" name="author[name]" value="John Smith"/>
  <input type="text" name="author[job]"  value="Legendary Pirate"/>
</form>

JavaScript:

$('form').serializeJSON();

// returns =>
{
  title: "Finding Loot",
  author: {
    name: "John Smith",
    job: "Legendary Pirate"
  }
}

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="fullName"              value="Mario Izquierdo" />

  <!-- 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>

  <!-- 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>
	</select>
</form>

JavaScript:

$('#my-profile').serializeJSON();

// returns =>
{
  fullName: "Mario Izquierdo",

  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.

All attribute values are strings by default. But you can force values to be parsed with specific types by appending the type with a colon.

<form>
  <input type="text" name="strbydefault"     value=":string is the default (implicit) type"/>
  <input type="text" name="text:string"      value=":string type can still be used to overrid other parsing options"/>
  <input type="text" name="excluded:skip"    value="Use :skip to not include this field in the result"/>

  <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 stuff]:number" value="other stuff"/>

  <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 stuff]:null"     value="other stuff"/>

  <input type="text" name="autos[string]:auto"          value="text with stuff"/>
  <input type="text" name="autos[0]:auto"               value="0"/>
  <input type="text" name="autos[1]:auto"               value="1"/>
  <input type="text" name="autos[true]:auto"            value="true"/>
  <input type="text" name="autos[false]:auto"           value="false"/>
  <input type="text" name="autos[null]:auto"            value="null"/>
  <input type="text" name="autos[list]:auto"            value="[1, 2, 3]"/>

  <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"}'/>
</form>

$('form').serializeJSON();

// returns =>
{
  "strbydefault": ":string is the default (implicit) type",
  "text": ":string type can still be used to overrid other parsing options",
  // excluded:skip is not included in the output
  "numbers": {
    "1": 1,
    "1.1": 1.1,
    "other stuff": NaN, // <-- Not a Number
  },
  "bools": {
    "true": true,
    "false": false,
    "0": false, // <-- "false", "null", "undefined", "", "0" parse as false
  },
  "nulls": {
    "null": null, // <-- "false", "null", "undefined", "", "0" parse as null
    "other stuff": "other stuff"
  },
  "autos": { // <-- works like the parseAll option
    "string": "text with stuff",
    "0": 0,         // <-- parsed as number
    "1": 1,         // <-- parsed as number
    "true": true,   // <-- parsed as boolean
    "false": false, // <-- parsed as boolean
    "null": null,   // <-- parsed as null
    "list": "[1, 2, 3]" // <-- array and object types are not auto-parsed
  },
  "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 having to add the ":type" suffix:

<form>
  <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="anauto"  data-value-type="auto"    value="0"/>
</form>

By default .serializeJSON() with no options has this behavior:

• Values are always strings (unless appending :types to the input names)
• 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)

This is because serializeJSON is designed to return exactly the same as a regular HTML form submission when serialized as Rack/Rails params, which ensures maximun compatibility and stability.

Allowed options to change the default behavior:

• checkboxUncheckedValue: string, string value used on unchecked checkboxes (otherwise those values are ignored). For example {checkboxUncheckedValue: ""}. If the value needs to be parsed (i.e. to a Boolean or Null) use a parse option (i.e. parseBooleans: true) or define the input with the :boolean or :null types.
• parseBooleans: true, automatically detect and convert strings "true" and "false" to booleans true and false.
• parseNumbers: true, automatically detect and convert strings like "1", "33.33", "-44" to numbers like 1, 33.33, -44.
• parseNulls: true, automatically detect and convert the string "null" to the null value null.
• parseAll: true, all of the above. This is the same as if the default :type was :auto instead of :string.
• parseWithFunction: function, define your own parse function(inputValue, inputName) { return parsedValue }.
• 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 is 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 :types or override the default types. Defined as an object like { type: function(value){...} }. For example: {customTypes: {nullable: function(str){ return str || null; }}.
• defaultTypes: {defaultTypes}, in case you want to re-define all the :types. Defined as an object like { type: function(value){...} }
• 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"}).

More info about options usage in the sections below.

In my opinion, the most confusing detail when serializing a form is the input type checkbox, that will include the value if checked, and nothing if unchecked.

To deal with this, it is a common practice 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 it is unobtrusive and ensures progressive enhancement, because it is the standard HTML behavior (also works without JavaScript).

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

For example:

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

Serializes like this by default:

$('form').serializeJSON();

// returns =>
{'check1': 'true'} // Note that check2 and check3 are not included because they are not checked

Which ignores any unchecked checkboxes. To include all checkboxes, use the checkboxUncheckedValue option like this:

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

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

The "unchecked" value can also be specified via the HTML attribute data-unchecked-value (Note this attribute is only recognized by the plugin):

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

  <input type="checkbox" name="unchecked[bool]"  value="true" data-unchecked-value="false" />
  <input type="checkbox" name="unchecked[bin]"   value="1"    data-unchecked-value="0" />
  <input type="checkbox" name="unchecked[cool]"  value="YUP" /> <!-- No unchecked value specified -->
</form>

Serializes like this by default:

$('form#checkboxes').serializeJSON(); // Note no option is used

// returns =>
{
  'checked': {
    'bool':  'true',
    'bin':   '1',
    'cool':  'YUP'
  },
  'unchecked': {
    'bool': 'false',
    'bin':  '0'
    // Note that unchecked cool does not appear, 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 attribute has precedence over the option. And remember that you can combine it with other options to parse values as well.

$('form#checkboxes').serializeJSON({checkboxUncheckedValue: 'NOPE', parseBooleans: true, parseNumbers: true});

// returns =>
{
  'checked': {
    'bool':  true,
    'bin':   1,
    'cool':  'YUP'
  },
  'unchecked': {
    'bool': false, // value from data-unchecked-value attribute, and parsed with parseBooleans
    'bin':  0,     // value from data-unchecked-value attribute, and parsed with parseNumbers
    'cool': 'NOPE' // value from checkboxUncheckedValue option
  }
}

The default type is :string, so all values are Strings by default, even if they look like booleans, numbers or nulls. For example:

<form>
  <input type="text" name="bool[true]"    value="true"/>
  <input type="text" name="bool[false]"   value="false"/>
  <input type="text" name="number[0]"     value="0"/>
  <input type="text" name="number[1]"     value="1"/>
  <input type="text" name="number[2.2]"   value="2.2"/>
  <input type="text" name="number[-2.25]" value="-2.25"/>
  <input type="text" name="null"          value="null"/>
  <input type="text" name="string"        value="text is always string"/>
  <input type="text" name="empty"         value=""/>
</form>

$('form').serializeJSON();

// returns =>
{
  "bool": {
    "true": "true",
    "false": "false",
  }
  "number": {
    "0": "0",
    "1": "1",
    "2.2": "2.2",
    "-2.25": "-2.25",
  }
  "null": "null",
  "string": "text is always string",
  "empty": ""
}

Note that all values are strings.

To auto-detect types, you could use the :auto type (append :auto to input name). Or, you could use the parse options. For example, to parse nulls and numbers:

$('form').serializeJSON({parseNulls: true, parseNumbers: true});

// returns =>
{
  "bool": {
    "true": "true", // booleans are still strings, because parseBooleans was not set
    "false": "false",
  }
  "number": {
    "0": 0, // numbers are parsed because parseNumbers: true
    "1": 1,
    "2.2": 2.2,
    "-2.25": -2.25,
  }
  "null": null, // "null" strings are converted to null becase parseNulls: true
  "string": "text is always string",
  "empty": ""
}

For rare cases, a custom parser can be defined with a function:

var emptyStringsAndZerosToNulls = function(val, inputName) {
  if (val === "") return null; // parse empty strings as nulls
  if (val === 0)  return null; // parse 0 as null
  return val;
}

$('form').serializeJSON({parseWithFunction: emptyStringsAndZerosToNulls, parseNumbers: true});

// returns =>
{
  "bool": {
    "true": "true",
    "false": "false",
  }
  "number": {
    "0": null, // <-- parsed with custom function
    "1": 1,
    "2.2": 2.2,
    "-2.25": -2.25,
  }
  "null": "null",
  "string": "text is always string",
  "empty": null // <-- parsed with custom function
}

You can define your own types or override the defaults with the customTypes option. For example:

<form>
  <input type="text" name="scary:alwaysBoo" value="not boo"/>
  <input type="text" name="str:string"      value="str"/>
  <input type="text" name="number:number"   value="5"/>
</form>

$('form').serializeJSON({
  customTypes: {
    alwaysBoo: function(str) { // value is always a string
      return "boo";
    },
    string: function(str) { // all strings will now end with " override"
      return str + " override";
    }
  }
});

// returns =>
{
  "scary": "boo",        // <-- parsed with type :alwaysBoo
  "str": "str override", // <-- parsed with new type :string (instead of the default)
  "number": 5,           // <-- the default :number still works
}

The default types are defined in $.serializeJSON.defaultOptions.defaultTypes. If you want to define your own set of types, you could also re-define that option (it will not override the types, but define a new set of types).

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
      }).serializeJSON();

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)).

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

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

$('form').serializeJSON();

// 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.

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.parseAll = true; // parse booleans, numbers and nulls by default

$('form').serializeJSON(); // No options => then use $.serializeJSON.defaultOptions

// returns =>
{
  "bool": {
    "true": true,
    "false": false,
  }
  "number": {
    "0": 0,
    "1": 1,
    "2.2": 2.2,
    "-2.25": -2.25,
  }
  "null": null,
  "string": "text is always string",
  "empty": ""
}

I found others solving the same problem:

• https://github.com/macek/jquery-serialize-object
• https://github.com/hongymagic/jQuery.serializeObject
• https://github.com/danheberden/jquery-serializeForm
• https://github.com/maxatwork/form2js (plain js, no jQuery)
• https://github.com/serbanghita/formToObject.js (plain js, no jQuery)
• https://gist.github.com/shiawuen/2634143 (simpler but small)

But none of them checked what I needed at the time serializeJSON was created. Factors that differentiate serializeJSON from most of 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.

• 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