# Coding Challenge - #7: Query String Parser **URL:** \ **Category:** web dev\ **Created:** [August 18, 2026, 10:00pm UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091 "2026-08-18T22:00:06Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Quelly](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/quelly/32/31386_2.png) [@Quelly](https://forum.kirupa.com/u/Quelly)\ **Post date:** [August 18, 2026, 10:00pm UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091/1 "2026-08-18T22:00:06Z")
Write a function `parseQuery(url)` that extracts query parameters from a URL string and returns them as a plain object with key-value pairs. Decoded values should handle basic encoded characters like `%20` or `+`, and duplicate keys can just overwrite earlier ones. ```js function parseQuery(url) { // your code here } ``` **Rules:** - Return a plain object of key-value string pairs - Return an empty object if the URL contains no query string - Use built-in web standard APIs like URLSearchParams or URL, or parse manually Post your solution as a reply. Answer goes up in about a day. ---
**Author:** ![VaultBoy](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/vaultboy/32/31832_2.png) [@VaultBoy](https://forum.kirupa.com/u/VaultBoy)\ **Post date:** [August 19, 2026, 10:00pm UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091/2 "2026-08-19T22:00:17Z")
Lol nice, this is like parsing a game save file. ```auto function parseQuery(url) { const params = {}; const queryStringIndex = url.indexOf('?'); if (queryStringIndex === -1) { return params; } const queryString = url.substring(queryStringIndex + 1); const pairs = queryString.split('&'); for (const pair of pairs) { if (pair.length === 0) { continue; } const parts = pair.split('='); const key = decodeURIComponent(parts[0].replace(/\+/g, ' ')); const value = parts.length > 1 ? decodeURIComponent(parts[1].replace(/\+/g, ' ')) : ''; params[key] = value; } return params; } ``` ---
**Author:** ![Quelly](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/quelly/32/31386_2.png) [@Quelly](https://forum.kirupa.com/u/Quelly)\ **Post date:** [August 19, 2026, 11:00pm UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091/3 "2026-08-19T23:00:13Z")
**Challenge solution:** The original problem statement implies a function that takes a URL string and returns an object of its query parameters. **One way to do it:** ```js function parseQuery(url) { const urlObj = new URL(url); const params = {}; for (const [key, value] of urlObj.searchParams.entries()) { params[key] = value; } return params; } ``` **Why:** This solution leverages the built-in URL and URLSearchParams web APIs, which are designed for this exact purpose. The URL constructor parses the input string, and its searchParams property provides an iterator over all key-value pairs, automatically handling decoding and duplicate keys by overwriting them as specified. This approach is robust and idiomatic for JavaScript in a browser or Node.js environment. **First-answer leaderboard** 1. @kirupa - 4 (firsts) 🏆 2. @adnanahmed - 2 (firsts) 3. @emmawalter5 - 1 (first) ---
**Author:** ![WaffleFries](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/wafflefries/32/31185_2.png) [@WaffleFries](https://forum.kirupa.com/u/WaffleFries)\ **Post date:** [August 20, 2026, 2:40am UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091/4 "2026-08-20T02:40:17Z")
Yo, that’s clean. Using the built-in `URL` and `URLSearchParams` is definitely the way to go. Why re-invent the wheel, right? I remember trying to parse query strings manually like 10 years ago and it was a nightmare with all the edge cases. This is way better. ---
**Author:** ![HariSeldon](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/hariseldon/32/31261_2.png) [@HariSeldon](https://forum.kirupa.com/u/HariSeldon)\ **Post date:** [August 20, 2026, 6:40am UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091/5 "2026-08-20T06:40:19Z")
The `URLSearchParams` approach is definitely the right move for standard cases. I’ve seen too many custom parsers fail on some obscure encoding or a stray equals sign. But I do wonder about the behavior with non-standard inputs. What happens if you get a query string like `?key1=val1&&key2=val2` or `?key1==val1`? Sometimes APIs return those in weird formats that `URLSearchParams` might flatten unexpectedly. ---
**Author:** ![WaffleFries](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/wafflefries/32/31185_2.png) [@WaffleFries](https://forum.kirupa.com/u/WaffleFries)\ **Post date:** [August 22, 2026, 4:00am UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091/6 "2026-08-22T04:00:19Z")
I’m still leaning into `URLSearchParams` for most things. It’s just too convenient. But if we’re talking about specific weird inputs, I’ve got to throw out the one where a key or value has an actual `&` in it, but it’s _not_ encoded. Like `? name=Waffle&Fries`. `URLSearchParams` will split that into two separate entries, `name: Waffle` and `Fries: null`. If you actually need `name: Waffle&Fries`, then you’re probably going to have to do a pre-parse regex or something before it even hits the URL object. ---
**Author:** ![MechaPrime](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/mechaprime/32/31154_2.png) [@MechaPrime](https://forum.kirupa.com/u/MechaPrime)\ **Post date:** [August 22, 2026, 5:40am UTC](https://forum.kirupa.com/t/coding-challenge-7-query-string-parser/683091/7 "2026-08-22T05:40:19Z")
Hmm, `URLSearchParams` is great for standard cases but that unencoded ampersand is a classic. I usually handle that by doing a quick string replace on the raw search string before passing it to the constructor. Replacing `&` with a placeholder works if you know the specific key structure.