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A stricter Query String parser

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A stricter query string parser allows to ensure URIs uniqueness and better caching through your own cache but also public HTTP proxies for public endpoints.

To ensure URIs uniqueness, strict-qs checks:

  • the order in which query strings are set,
  • query parameters values aren't set to their default values,
  • values set are reentrant (ie: 1.10 will be refused, its canonical form 1.1 will be required),
  • query parameters used are existing and effective,
  • items collections are sorted (by value for number, alpha-numeric for strings).

As a side effect, it also cast values from strings to their target types.

You may wonder if it is not overkill to be that strict. On every projects I worked on, I never been sad to have built too strict systems. The inverse is not true ;).

Also, it may be less pain to handle such strictness if you generate client APIs that handle that strictness for you, which is recommended. You can see an example of such client here.


import qs from 'strict-qs';

// The definition formatting is swagger compatible
// but only for the subset I use. PRs are welcome
// for broader support
const qsDefinition = [{
  name: 'lang',
  in: 'query',
  type: 'string',
  required: true,
  description: 'The language for the search'
}, {
  name: 'types',
  in: 'query',
  type: 'array',
  items: {
    type: 'string',
    enum: ['open', 'closed', 'pending', 'idle', 'invalid'],
  description: 'The types of the search'
}, {
  name: 'code',
  in: 'query',
  type: 'integer',
  description: 'The code id'

// Returns
  lang: 'fr',
  types: ['open', 'closed', 'pending'],
  code: 3

// throws an error since the order is bad
new Error('E_BAD_QUERY_PARAM', 'types')

The returned query parameters should still be validated with any JSON Schema validator. You can see how it is done in swagger-http-router for instance.


qsStrict(definitions, search) ⇒ Object

Parse a queryString according to the provided definitions

Kind: global function
Returns: Object - The parsed properties

Param Type Description
definitions Array Swagger compatible list of defitions
search string The actual query string to parse


import qs from 'strict-qs';

const qsDefinition = [{
  name: 'pages',
  in: 'query',
  type: 'array',
  items: {
    type: 'number',
  ordered: true,
  description: 'The pages to print',

qs(qsDefinition, '?pages=0&pages=1&pages=2');
// Returns:
// {
//  pages: [0, 1, 2], // eslint-disable-line
// }