javascript 43 lines · 7 steps

Syncing search state with the URL hash in React

A React search box keeps its query in the URL hash, debounces the sync, and scrolls to the matching section.

Explained by highlit
React Intermediate debouncing url-state useeffect refs controlled-input
1import { useState, useEffect, useRef } from 'react';
2 
3export function SectionSearch({ sections }) {
4 const [query, setQuery] = useState(() => decodeURIComponent(window.location.hash.slice(1)));
5 const debounceRef = useRef(null);
6 
7 useEffect(() => {
8 clearTimeout(debounceRef.current);
9 debounceRef.current = setTimeout(() => {
10 const next = query ? `#${encodeURIComponent(query)}` : ' ';
11 window.history.replaceState(null, '', next);
12 }, 250);
13 return () => clearTimeout(debounceRef.current);
14 }, [query]);
15 
16 useEffect(() => {
17 if (!query) return;
18 const match = sections.find((s) =>
19 s.title.toLowerCase().includes(query.toLowerCase())
20 );
21 if (!match) return;
22 const el = document.getElementById(match.id);
23 el?.scrollIntoView({ behavior: 'smooth', block: 'start' });
24 }, [query, sections]);
25 
26 useEffect(() => {
27 const onHashChange = () => {
28 setQuery(decodeURIComponent(window.location.hash.slice(1)));
29 };
30 window.addEventListener('hashchange', onHashChange);
31 return () => window.removeEventListener('hashchange', onHashChange);
32 }, []);
33 
34 return (
35 <input
36 type="search"
37 value={query}
38 onChange={(e) => setQuery(e.target.value)}
39 placeholder="Jump to section..."
40 aria-label="Search sections"
41 />
42 );
43}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Seeding state from the URL makes a component's view sharable and restorable across reloads.
  2. 2A ref holding a timer id lets you debounce side effects and cancel them cleanly on unmount.
  3. 3Listening for hashchange closes the loop so browser navigation feeds back into component state.

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