query-string

What is query-string?

The query-string npm package is used for parsing and stringifying URL query strings. It provides a simple API for dealing with query strings in a way that is both convenient and cross-browser compatible.

What are query-string's main functionalities?

Parsing query strings

This feature allows you to parse a query string into an object. It automatically handles various edge cases and decoding of parameters.

const queryString = require('query-string');
const parsed = queryString.parse('?foo=bar');
console.log(parsed); //=> {foo: 'bar'}

Stringifying objects

This feature enables you to take an object and convert it into a URL query string. It ensures that keys and values are properly encoded.

const queryString = require('query-string');
const stringified = queryString.stringify({foo: 'bar'});
console.log(stringified); //=> 'foo=bar'

Extracting query strings

This function extracts the query string from a URL.

const queryString = require('query-string');
const extracted = queryString.extract('http://example.com/?foo=bar');
console.log(extracted); //=> '?foo=bar'

Parsing arrays and objects

The package can parse query strings with array and object syntax, turning them into the corresponding JavaScript structures.

const queryString = require('query-string');
const parsed = queryString.parse('?foo[]=bar&foo[]=baz');
console.log(parsed); //=> {foo: ['bar', 'baz']}

Other packages similar to query-string

qs

The 'qs' package is a query string parser with nesting support. It is more feature-rich than query-string, allowing for complex structures like nested objects and arrays. However, it might be overkill for simple use cases.

url-search-params

This is a polyfill for the URLSearchParams API which is built into modern browsers. It provides similar functionality to query-string but is designed to mimic the native browser API.

querystringify

querystringify is a small and simple query string parser and stringifier. It is focused on speed and simplicity, and while it has fewer features than query-string, it may be faster in some cases.

README

query-string

Parse and stringify URL query strings

---

^{My open source work is supported by the community}

^{Special thanks to:}

Strapi is the leading open-source headless CMS.

^{It’s 100% JavaScript, fully customizable, and developer-first.}

---

Install

npm install query-string

Not npm install querystring!!!!!

For browser usage, this package targets the latest version of Chrome, Firefox, and Safari.

Usage

import queryString from 'query-string';

console.log(location.search);
//=> '?foo=bar'

const parsed = queryString.parse(location.search);
console.log(parsed);
//=> {foo: 'bar'}

console.log(location.hash);
//=> '#token=bada55cafe'

const parsedHash = queryString.parse(location.hash);
console.log(parsedHash);
//=> {token: 'bada55cafe'}

parsed.foo = 'unicorn';
parsed.ilike = 'pizza';

const stringified = queryString.stringify(parsed);
//=> 'foo=unicorn&ilike=pizza'

location.search = stringified;
// note that `location.search` automatically prepends a question mark
console.log(location.search);
//=> '?foo=unicorn&ilike=pizza'

API

.parse(string, options?)

Parse a query string into an object. Leading ? or # are ignored, so you can pass location.search or location.hash directly.

The returned object is created with Object.create(null) and thus does not have a prototype.

options

Type: object

decode

Type: boolean
Default: true

Decode the keys and values. URL components are decoded with decode-uri-component.

arrayFormat

Type: string
Default: 'none'

• 'bracket': Parse arrays with bracket representation:

import queryString from 'query-string';

queryString.parse('foo[]=1&foo[]=2&foo[]=3', {arrayFormat: 'bracket'});
//=> {foo: ['1', '2', '3']}

• 'index': Parse arrays with index representation:

import queryString from 'query-string';

queryString.parse('foo[0]=1&foo[1]=2&foo[3]=3', {arrayFormat: 'index'});
//=> {foo: ['1', '2', '3']}

• 'comma': Parse arrays with elements separated by comma:

import queryString from 'query-string';

queryString.parse('foo=1,2,3', {arrayFormat: 'comma'});
//=> {foo: ['1', '2', '3']}

• 'separator': Parse arrays with elements separated by a custom character:

import queryString from 'query-string';

queryString.parse('foo=1|2|3', {arrayFormat: 'separator', arrayFormatSeparator: '|'});
//=> {foo: ['1', '2', '3']}

• 'bracket-separator': Parse arrays (that are explicitly marked with brackets) with elements separated by a custom character:

import queryString from 'query-string';

queryString.parse('foo[]', {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> {foo: []}

queryString.parse('foo[]=', {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> {foo: ['']}

queryString.parse('foo[]=1', {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> {foo: ['1']}

queryString.parse('foo[]=1|2|3', {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> {foo: ['1', '2', '3']}

queryString.parse('foo[]=1||3|||6', {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> {foo: ['1', '', 3, '', '', '6']}

queryString.parse('foo[]=1|2|3&bar=fluffy&baz[]=4', {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> {foo: ['1', '2', '3'], bar: 'fluffy', baz:['4']}

• 'colon-list-separator': Parse arrays with parameter names that are explicitly marked with :list:

import queryString from 'query-string';

queryString.parse('foo:list=one&foo:list=two', {arrayFormat: 'colon-list-separator'});
//=> {foo: ['one', 'two']}

• 'none': Parse arrays with elements using duplicate keys:

import queryString from 'query-string';

queryString.parse('foo=1&foo=2&foo=3');
//=> {foo: ['1', '2', '3']}

arrayFormatSeparator

Type: string
Default: ','

The character used to separate array elements when using {arrayFormat: 'separator'}.

sort

Type: Function | boolean
Default: true

Supports both Function as a custom sorting function or false to disable sorting.

parseNumbers

Type: boolean
Default: false

import queryString from 'query-string';

queryString.parse('foo=1', {parseNumbers: true});
//=> {foo: 1}

Parse the value as a number type instead of string type if it's a number.

parseBooleans

Type: boolean
Default: false

import queryString from 'query-string';

queryString.parse('foo=true', {parseBooleans: true});
//=> {foo: true}

Parse the value as a boolean type instead of string type if it's a boolean.

.stringify(object, options?)

Stringify an object into a query string and sorting the keys.

options

Type: object

strict

Type: boolean
Default: true

Strictly encode URI components with strict-uri-encode. It uses encodeURIComponent if set to false. You probably don't care about this option.

encode

Type: boolean
Default: true

URL encode the keys and values.

arrayFormat

Type: string
Default: 'none'

• 'bracket': Serialize arrays using bracket representation:

import queryString from 'query-string';

queryString.stringify({foo: [1, 2, 3]}, {arrayFormat: 'bracket'});
//=> 'foo[]=1&foo[]=2&foo[]=3'

• 'index': Serialize arrays using index representation:

import queryString from 'query-string';

queryString.stringify({foo: [1, 2, 3]}, {arrayFormat: 'index'});
//=> 'foo[0]=1&foo[1]=2&foo[2]=3'

• 'comma': Serialize arrays by separating elements with comma:

import queryString from 'query-string';

queryString.stringify({foo: [1, 2, 3]}, {arrayFormat: 'comma'});
//=> 'foo=1,2,3'

queryString.stringify({foo: [1, null, '']}, {arrayFormat: 'comma'});
//=> 'foo=1,,'
// Note that typing information for null values is lost
// and `.parse('foo=1,,')` would return `{foo: [1, '', '']}`.

• 'separator': Serialize arrays by separating elements with a custom character:

import queryString from 'query-string';

queryString.stringify({foo: [1, 2, 3]}, {arrayFormat: 'separator', arrayFormatSeparator: '|'});
//=> 'foo=1|2|3'

• 'bracket-separator': Serialize arrays by explicitly post-fixing array names with brackets and separating elements with a custom character:

import queryString from 'query-string';

queryString.stringify({foo: []}, {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> 'foo[]'

queryString.stringify({foo: ['']}, {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> 'foo[]='

queryString.stringify({foo: [1]}, {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> 'foo[]=1'

queryString.stringify({foo: [1, 2, 3]}, {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> 'foo[]=1|2|3'

queryString.stringify({foo: [1, '', 3, null, null, 6]}, {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> 'foo[]=1||3|||6'

queryString.stringify({foo: [1, '', 3, null, null, 6]}, {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|', skipNull: true});
//=> 'foo[]=1||3|6'

queryString.stringify({foo: [1, 2, 3], bar: 'fluffy', baz: [4]}, {arrayFormat: 'bracket-separator', arrayFormatSeparator: '|'});
//=> 'foo[]=1|2|3&bar=fluffy&baz[]=4'

• 'colon-list-separator': Serialize arrays with parameter names that are explicitly marked with :list:

import queryString from 'query-string';

queryString.stringify({foo: ['one', 'two']}, {arrayFormat: 'colon-list-separator'});
//=> 'foo:list=one&foo:list=two'

• 'none': Serialize arrays by using duplicate keys:

import queryString from 'query-string';

queryString.stringify({foo: [1, 2, 3]});
//=> 'foo=1&foo=2&foo=3'

arrayFormatSeparator

Type: string
Default: ','

The character used to separate array elements when using {arrayFormat: 'separator'}.

sort

Type: Function | boolean

Supports both Function as a custom sorting function or false to disable sorting.

import queryString from 'query-string';

const order = ['c', 'a', 'b'];

queryString.stringify({a: 1, b: 2, c: 3}, {
	sort: (a, b) => order.indexOf(a) - order.indexOf(b)
});
//=> 'c=3&a=1&b=2'

import queryString from 'query-string';

queryString.stringify({b: 1, c: 2, a: 3}, {sort: false});
//=> 'b=1&c=2&a=3'

If omitted, keys are sorted using Array#sort(), which means, converting them to strings and comparing strings in Unicode code point order.

skipNull

Skip keys with null as the value.

Note that keys with undefined as the value are always skipped.

Type: boolean
Default: false

import queryString from 'query-string';

queryString.stringify({a: 1, b: undefined, c: null, d: 4}, {
	skipNull: true
});
//=> 'a=1&d=4'

import queryString from 'query-string';

queryString.stringify({a: undefined, b: null}, {
	skipNull: true
});
//=> ''

skipEmptyString

Skip keys with an empty string as the value.

Type: boolean
Default: false

import queryString from 'query-string';

queryString.stringify({a: 1, b: '', c: '', d: 4}, {
	skipEmptyString: true
});
//=> 'a=1&d=4'

import queryString from 'query-string';

queryString.stringify({a: '', b: ''}, {
	skipEmptyString: true
});
//=> ''

.extract(string)

Extract a query string from a URL that can be passed into .parse().

Note: This behaviour can be changed with the skipNull option.

.parseUrl(string, options?)

Extract the URL and the query string as an object.

Returns an object with a url and query property.

If the parseFragmentIdentifier option is true, the object will also contain a fragmentIdentifier property.

import queryString from 'query-string';

queryString.parseUrl('https://foo.bar?foo=bar');
//=> {url: 'https://foo.bar', query: {foo: 'bar'}}

queryString.parseUrl('https://foo.bar?foo=bar#xyz', {parseFragmentIdentifier: true});
//=> {url: 'https://foo.bar', query: {foo: 'bar'}, fragmentIdentifier: 'xyz'}

options

Type: object

The options are the same as for .parse().

Extra options are as below.

parseFragmentIdentifier

Parse the fragment identifier from the URL.

Type: boolean
Default: false

import queryString from 'query-string';

queryString.parseUrl('https://foo.bar?foo=bar#xyz', {parseFragmentIdentifier: true});
//=> {url: 'https://foo.bar', query: {foo: 'bar'}, fragmentIdentifier: 'xyz'}

.stringifyUrl(object, options?)

Stringify an object into a URL with a query string and sorting the keys. The inverse of .parseUrl()

The options are the same as for .stringify().

Returns a string with the URL and a query string.

Query items in the query property overrides queries in the url property.

The fragmentIdentifier property overrides the fragment identifier in the url property.

queryString.stringifyUrl({url: 'https://foo.bar', query: {foo: 'bar'}});
//=> 'https://foo.bar?foo=bar'

queryString.stringifyUrl({url: 'https://foo.bar?foo=baz', query: {foo: 'bar'}});
//=> 'https://foo.bar?foo=bar'

queryString.stringifyUrl({
	url: 'https://foo.bar',
	query: {
		top: 'foo'
	},
	fragmentIdentifier: 'bar'
});
//=> 'https://foo.bar?top=foo#bar'

object

Type: object

url

Type: string

The URL to stringify.

query

Type: object

Query items to add to the URL.

.pick(url, keys, options?)

.pick(url, filter, options?)

Pick query parameters from a URL.

Returns a string with the new URL.

import queryString from 'query-string';

queryString.pick('https://foo.bar?foo=1&bar=2#hello', ['foo']);
//=> 'https://foo.bar?foo=1#hello'

queryString.pick('https://foo.bar?foo=1&bar=2#hello', (name, value) => value === 2, {parseNumbers: true});
//=> 'https://foo.bar?bar=2#hello'

.exclude(url, keys, options?)

.exclude(url, filter, options?)

Exclude query parameters from a URL.

Returns a string with the new URL.

import queryString from 'query-string';

queryString.exclude('https://foo.bar?foo=1&bar=2#hello', ['foo']);
//=> 'https://foo.bar?bar=2#hello'

queryString.exclude('https://foo.bar?foo=1&bar=2#hello', (name, value) => value === 2, {parseNumbers: true});
//=> 'https://foo.bar?foo=1#hello'

url

Type: string

The URL containing the query parameters to filter.

keys

Type: string[]

The names of the query parameters to filter based on the function used.

filter

Type: (key, value) => boolean

A filter predicate that will be provided the name of each query parameter and its value. The parseNumbers and parseBooleans options also affect value.

options

Type: object

Parse options and stringify options.

Nesting

This module intentionally doesn't support nesting as it's not spec'd and varies between implementations, which causes a lot of edge cases.

You're much better off just converting the object to a JSON string:

import queryString from 'query-string';

queryString.stringify({
	foo: 'bar',
	nested: JSON.stringify({
		unicorn: 'cake'
	})
});
//=> 'foo=bar&nested=%7B%22unicorn%22%3A%22cake%22%7D'

However, there is support for multiple instances of the same key:

import queryString from 'query-string';

queryString.parse('likes=cake&name=bob&likes=icecream');
//=> {likes: ['cake', 'icecream'], name: 'bob'}

queryString.stringify({color: ['taupe', 'chartreuse'], id: '515'});
//=> 'color=taupe&color=chartreuse&id=515'

Falsy values

Sometimes you want to unset a key, or maybe just make it present without assigning a value to it. Here is how falsy values are stringified:

import queryString from 'query-string';

queryString.stringify({foo: false});
//=> 'foo=false'

queryString.stringify({foo: null});
//=> 'foo'

queryString.stringify({foo: undefined});
//=> ''

FAQ

Why is it parsing + as a space?

See this answer.