serializeJSON

Adds the method serializeJSON() to serialize a form into a JavaScript Object. Supports the same format for nested parameters that is used in Ruby on Rails.

Install

Install with npm npm install @syneto/serializejson, or just download the serializejson.js script.

Usage Example

HTML form:

<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"/>
</form>

JavaScript:

import { serializeJSON } from '@syneto/serializejson';
serializeJSON(document.querySelector('form'));

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

Nested attributes and arrays can be specified by naming fields with the syntax: name="attr[nested][nested]".

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>

  <!-- 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:

serializeJSON(document.querySelector('#my-profile'));

// 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 that plugin name was already taken.

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

The plugin serializes the same inputs supported by .serializeArray(), following 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:

<form>
  <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"}'/>
</form>

serializeJSON(document.querySelector('form'));

// 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:

<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="anarray" data-value-type="array"   value="[1, 2, 3]"/>
</form>

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 parsing functions. The parsing functions receive the input name as a string, and the DOM elment of the serialized input.

<form>
  <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"/>
</form>

serializeJSON(document.querySelector('form'), {
  customTypes: {
    alwaysBoo: (strVal, el) => {
      // strVal: is the input value as a string
      // el: is the dom element. $(el) would be the jQuery element
      return "boo"; // value returned in the serialization of this type
    },
  }
});

// returns =>
{
  "scary": "boo",  // <-- parsed with custom type "alwaysBoo"
  "str": "str",
  "five": 5,
}

The provided customTypes can include one of the detaultTypes to override the default behavior:

serializeJSON(document.querySelector('form'), {
  customTypes: {
    alwaysBoo: (strVal) => { return "boo"; },
    string: (strVal) => { return strVal + "-OVERDRIVE"; },
  }
});

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

Default types used by the plugin are defined in defaultBaseOptions.defaultTypes.

Options

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:

<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:

serializeJSON(document.querySelector('form'));

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

To include all checkboxes, use the checkboxUncheckedValue option:

serializeJSON(document.querySelector('form'), {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>

serializeJSON(document.querySelector('form#checkboxes')); // 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).

serializeJSON(document.querySelector('form#checkboxes'), {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).

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:

<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>

serializeJSON(document.querySelector('form'));

// 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:

serializeJSON(document.querySelector('form'), {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 defaultOptions. You can just modify it to avoid setting the option on every call to serializeJSON. For example:

import { setDefaultOptions } from "serializejson";

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

Changelog

See CHANGELOG.md

Author

Copyright (c) 2024 Syneto This is a plain JS version of jquery.serializeJSON by Mario Izquierdo.