Go's url.ParseQuery in TypeScript

How to use

Install via yarn add locutus and import: import { ParseQuery } from 'locutus/golang/url/ParseQuery'.

Or with CommonJS: const { ParseQuery } = require('locutus/golang/url/ParseQuery')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	ParseQuery('a=1&b=2&b=3')	{a: ['1'], b: ['2', '3']}
2	ParseQuery('q=go+lang&x=%2B')	{q: ['go lang'], x: ['+']}
3	ParseQuery('empty=&flag')	{empty: [''], flag: ['']}

Notes

• Parses URL-encoded key/value pairs into arrays per key.

Dependencies

This function uses the following Locutus functions:

• QueryUnescape (golang/url)

Here's what our current TypeScript equivalent to Go's url.ParseQuery looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

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import { QueryUnescape } from './QueryUnescape.ts'

type QueryValues = Record<string, string[]>

export function ParseQuery(query: string): QueryValues {
  //      discuss at: https://locutus.io/golang/url/ParseQuery
  // parity verified: Go 1.23
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Parses URL-encoded key/value pairs into arrays per key.
  //       example 1: ParseQuery('a=1&b=2&b=3')
  //       returns 1: {a: ['1'], b: ['2', '3']}
  //       example 2: ParseQuery('q=go+lang&x=%2B')
  //       returns 2: {q: ['go lang'], x: ['+']}
  //       example 3: ParseQuery('empty=&flag')
  //       returns 3: {empty: [''], flag: ['']}

  const raw = String(query)
  if (raw === '') {
    return {}
  }

  const out: QueryValues = {}
  const pairs = raw.split('&')

  for (const pair of pairs) {
    if (pair === '') {
      continue
    }

    const separator = pair.indexOf('=')
    const keyRaw = separator >= 0 ? pair.slice(0, separator) : pair
    const valueRaw = separator >= 0 ? pair.slice(separator + 1) : ''
    const key = QueryUnescape(keyRaw)
    const value = QueryUnescape(valueRaw)

    const existing = out[key]
    if (existing) {
      existing.push(value)
    } else {
      out[key] = [value]
    }
  }

  return out
}

import { QueryUnescape } from './QueryUnescape.ts'

export function ParseQuery(query) {
  //      discuss at: https://locutus.io/golang/url/ParseQuery
  // parity verified: Go 1.23
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Parses URL-encoded key/value pairs into arrays per key.
  //       example 1: ParseQuery('a=1&b=2&b=3')
  //       returns 1: {a: ['1'], b: ['2', '3']}
  //       example 2: ParseQuery('q=go+lang&x=%2B')
  //       returns 2: {q: ['go lang'], x: ['+']}
  //       example 3: ParseQuery('empty=&flag')
  //       returns 3: {empty: [''], flag: ['']}

  const raw = String(query)
  if (raw === '') {
    return {}
  }

  const out = {}
  const pairs = raw.split('&')

  for (const pair of pairs) {
    if (pair === '') {
      continue
    }

    const separator = pair.indexOf('=')
    const keyRaw = separator >= 0 ? pair.slice(0, separator) : pair
    const valueRaw = separator >= 0 ? pair.slice(separator + 1) : ''
    const key = QueryUnescape(keyRaw)
    const value = QueryUnescape(valueRaw)

    const existing = out[key]
    if (existing) {
      existing.push(value)
    } else {
      out[key] = [value]
    }
  }

  return out
}

// golang/url/QueryUnescape (Locutus dependency module)
function QueryUnescape(s: string): string {
  //      discuss at: https://locutus.io/golang/url/QueryUnescape
  // parity verified: Go 1.23
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Decodes query-escaped strings where `+` maps to a space.
  //       example 1: QueryUnescape('a+b%2Bc')
  //       returns 1: 'a b+c'
  //       example 2: QueryUnescape('https%3A%2F%2Flocutus.io%2F%3Fq%3Dgo+lang')
  //       returns 2: 'https://locutus.io/?q=go lang'
  //       example 3: QueryUnescape('%2Bplus')
  //       returns 3: '+plus'

  const raw = String(s).replace(/\+/g, ' ')
  try {
    return decodeURIComponent(raw)
  } catch {
    throw new TypeError('QueryUnescape(): invalid query escape')
  }
}

// golang/url/ParseQuery (target function module)
type QueryValues = Record<string, string[]>

function ParseQuery(query: string): QueryValues {
  //      discuss at: https://locutus.io/golang/url/ParseQuery
  // parity verified: Go 1.23
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Parses URL-encoded key/value pairs into arrays per key.
  //       example 1: ParseQuery('a=1&b=2&b=3')
  //       returns 1: {a: ['1'], b: ['2', '3']}
  //       example 2: ParseQuery('q=go+lang&x=%2B')
  //       returns 2: {q: ['go lang'], x: ['+']}
  //       example 3: ParseQuery('empty=&flag')
  //       returns 3: {empty: [''], flag: ['']}

  const raw = String(query)
  if (raw === '') {
    return {}
  }

  const out: QueryValues = {}
  const pairs = raw.split('&')

  for (const pair of pairs) {
    if (pair === '') {
      continue
    }

    const separator = pair.indexOf('=')
    const keyRaw = separator >= 0 ? pair.slice(0, separator) : pair
    const valueRaw = separator >= 0 ? pair.slice(separator + 1) : ''
    const key = QueryUnescape(keyRaw)
    const value = QueryUnescape(valueRaw)

    const existing = out[key]
    if (existing) {
      existing.push(value)
    } else {
      out[key] = [value]
    }
  }

  return out
}

// golang/url/QueryUnescape (Locutus dependency module)
function QueryUnescape(s) {
  //      discuss at: https://locutus.io/golang/url/QueryUnescape
  // parity verified: Go 1.23
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Decodes query-escaped strings where `+` maps to a space.
  //       example 1: QueryUnescape('a+b%2Bc')
  //       returns 1: 'a b+c'
  //       example 2: QueryUnescape('https%3A%2F%2Flocutus.io%2F%3Fq%3Dgo+lang')
  //       returns 2: 'https://locutus.io/?q=go lang'
  //       example 3: QueryUnescape('%2Bplus')
  //       returns 3: '+plus'

  const raw = String(s).replace(/\+/g, ' ')
  try {
    return decodeURIComponent(raw)
  } catch {
    throw new TypeError('QueryUnescape(): invalid query escape')
  }
}

// golang/url/ParseQuery (target function module)
function ParseQuery(query) {
  //      discuss at: https://locutus.io/golang/url/ParseQuery
  // parity verified: Go 1.23
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Parses URL-encoded key/value pairs into arrays per key.
  //       example 1: ParseQuery('a=1&b=2&b=3')
  //       returns 1: {a: ['1'], b: ['2', '3']}
  //       example 2: ParseQuery('q=go+lang&x=%2B')
  //       returns 2: {q: ['go lang'], x: ['+']}
  //       example 3: ParseQuery('empty=&flag')
  //       returns 3: {empty: [''], flag: ['']}

  const raw = String(query)
  if (raw === '') {
    return {}
  }

  const out = {}
  const pairs = raw.split('&')

  for (const pair of pairs) {
    if (pair === '') {
      continue
    }

    const separator = pair.indexOf('=')
    const keyRaw = separator >= 0 ? pair.slice(0, separator) : pair
    const valueRaw = separator >= 0 ? pair.slice(separator + 1) : ''
    const key = QueryUnescape(keyRaw)
    const value = QueryUnescape(valueRaw)

    const existing = out[key]
    if (existing) {
      existing.push(value)
    } else {
      out[key] = [value]
    }
  }

  return out
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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