2nd/10_Wiki/Topic_Programming/Architecture/Downshift.md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-downshift	Downshift	10_Wiki/Topics	verified	self	downshift-js useCombobox useSelect	none	A	0.9	applied	react ui accessibility combobox hooks		2026-05-10	pending	language framework typescript react

Downshift

매 한 줄

"매 headless UI 의 accessibility-first combobox primitive". Kent C. Dodds 의 2017 release, 매 render-prop / hook API 의 ARIA 1.2 combobox spec 의 implement. 매 2026 의 매 alternative 의 많음 (Radix, Headless UI, Ariakit, React Aria) 이지만 매 downshift 의 매 mature / battle-tested / tiny (~5KB).

매 핵심

매 무엇 의 solve

• 매 native <select> 의 styling 의 unable.
• 매 custom dropdown 의 매 keyboard / screen reader / focus management 의 hard.
• 매 ARIA roles (combobox, listbox, option) 의 correctly wire.

매 API 종류

• useCombobox — 매 typeahead 의 search input + dropdown.
• useSelect — 매 native select replacement (no input).
• useMultipleSelection — 매 tag / chip selection.
• Render-prop <Downshift> — 매 legacy, 매 hooks 권장.

매 핵심 state

• isOpen — dropdown open?
• highlightedIndex — 매 keyboard hover.
• selectedItem — 매 chosen value.
• inputValue — 매 typed text.

매 응용

1. Autocomplete / type-ahead search.
2. Country / timezone picker.
3. Multi-select tag input (with useMultipleSelection).
4. Async-loading dropdowns.

💻 패턴

Pattern 1: Basic useCombobox

import { useCombobox } from "downshift";
import { useState } from "react";

const ALL = ["apple","banana","cherry","date","elderberry"];

export function FruitCombo() {
  const [items, setItems] = useState(ALL);
  const cb = useCombobox({
    items,
    onInputValueChange: ({ inputValue }) => {
      setItems(ALL.filter(f => f.includes(inputValue?.toLowerCase() ?? "")));
    },
  });

  return (
    <div>
      <label {...cb.getLabelProps()}>Fruit</label>
      <input {...cb.getInputProps()} />
      <ul {...cb.getMenuProps()}>
        {cb.isOpen && items.map((item, i) => (
          <li
            key={item}
            {...cb.getItemProps({ item, index: i })}
            style={{ background: cb.highlightedIndex === i ? "#def" : "white" }}
          >{item}</li>
        ))}
      </ul>
    </div>
  );
}

Pattern 2: Async items (debounced)

import { useCombobox } from "downshift";
import { useState, useEffect } from "react";
import { useDebouncedValue } from "./hooks";

export function UserPicker() {
  const [query, setQuery] = useState("");
  const debounced = useDebouncedValue(query, 250);
  const [items, setItems] = useState<User[]>([]);

  useEffect(() => {
    if (!debounced) return;
    fetch(`/api/users?q=${debounced}`).then(r => r.json()).then(setItems);
  }, [debounced]);

  const cb = useCombobox({
    items,
    itemToString: u => u?.name ?? "",
    onInputValueChange: ({ inputValue }) => setQuery(inputValue ?? ""),
  });
  // 매 render UI 동일 패턴.
}

Pattern 3: Multi-select with chips

import { useCombobox, useMultipleSelection } from "downshift";

function TagInput({ all }: { all: string[] }) {
  const ms = useMultipleSelection<string>({});
  const remaining = all.filter(t => !ms.selectedItems.includes(t));
  const cb = useCombobox({
    items: remaining,
    onSelectedItemChange: ({ selectedItem }) => {
      if (selectedItem) ms.addSelectedItem(selectedItem);
    },
    selectedItem: null,
  });
  return (
    <div>
      {ms.selectedItems.map((t, i) => (
        <span key={t} {...ms.getSelectedItemProps({ selectedItem: t, index: i })}>
          {t} <button onClick={() => ms.removeSelectedItem(t)}>×</button>
        </span>
      ))}
      <input {...cb.getInputProps(ms.getDropdownProps())} />
      {/* menu... */}
    </div>
  );
}

Pattern 4: useSelect (no typing)

import { useSelect } from "downshift";

function SizeSelect() {
  const items = ["S","M","L","XL"];
  const sel = useSelect({ items });
  return (
    <>
      <button {...sel.getToggleButtonProps()}>
        {sel.selectedItem ?? "Pick size"}
      </button>
      <ul {...sel.getMenuProps()}>
        {sel.isOpen && items.map((s, i) => (
          <li key={s} {...sel.getItemProps({ item: s, index: i })}>{s}</li>
        ))}
      </ul>
    </>
  );
}

Pattern 5: Controlled state (Redux / Zustand)

const cb = useCombobox({
  items,
  selectedItem: store.selected,
  onSelectedItemChange: ({ selectedItem }) => store.set(selectedItem),
  inputValue: store.input,
  onInputValueChange: ({ inputValue }) => store.setInput(inputValue ?? ""),
});

Pattern 6: stateReducer for custom keyboard

import { useCombobox } from "downshift";
const stateReducer = (state, { type, changes }) => {
  switch (type) {
    case useCombobox.stateChangeTypes.InputKeyDownEnter:
    case useCombobox.stateChangeTypes.ItemClick:
      // 매 Enter 시 dropdown 의 close 하지 X
      return { ...changes, isOpen: state.isOpen, highlightedIndex: state.highlightedIndex };
    default: return changes;
  }
};

매 결정 기준

상황	Approach
React + ARIA combobox	downshift
Full design system (Modal, Tabs, etc.)	Radix UI / Ariakit
Adobe quality + i18n	React Aria
Tailwind + simple primitives	Headless UI
Vue / Svelte	downshift X — find native

기본값: 매 React combobox 만 필요 시 downshift, 매 design system 전체 시 Radix.

🔗 Graph

• 부모: React · Headless UI · Accessibility (A11y)
• 변형: Radix UI · Ariakit
• 응용: Autocomplete
• Adjacent: Render_Props

🤖 LLM 활용

언제: 매 React typeahead / select 의 build, 매 a11y 의 mandatory. 언제 X: 매 native select 의 충분, 매 React 외 framework.

❌ 안티패턴

• Custom keyboard 의 reinvent: 매 stateReducer 로 override 의 의도된 path.
• State sync mistakes: 매 controlled / uncontrolled 의 mix — 매 하나의 choose.
• getXxxProps 의 spread 의 omit: 매 ARIA attrs 의 lost — 매 a11y 의 break.

🧪 검증 / 중복

• Verified (downshift v9 docs, ARIA 1.2 combobox pattern, GitHub 11k+ stars).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — useCombobox + useSelect + multi-select