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

Install

$ npm install query-string

This module targets Node.js 6 or later and the latest version of Chrome, Firefox, and Safari. If you want support for older browsers, or, if your project is using create-react-app v1, use version 5: npm install query-string@5.

Usage

const queryString = require('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:

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

• 'index': Parse arrays with index representation:

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:

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

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

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

sort

Type: Function | boolean
Default: true

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

parseNumbers

Type: boolean
Default: false

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

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:

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

• 'index': Serialize arrays using index representation:

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:

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

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

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

sort

Type: Function | boolean

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

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'

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.

.extract(string)

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

.parseUrl(string, options?)

Extract the URL and the query string as an object.

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

Returns an object with a url and query property.

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

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:

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:

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:

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

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

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

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