Skip to content

KRWAmount (custom — display-only currency formatter) — spec

Custom component pattern. Display-only counterpart to AmountInput. Renders KRW amounts consistently across the app — receipts, balances, transaction details, summaries.

Purpose

Formats and displays a KRW amount with the right separator, suffix/prefix, sign, and color. Read-only. Use everywhere money is displayed but not entered.

Why a separate component (not just formatKRW(...))

A centralized component: - Consistent formatting across the entire app. - Single place to switch convention (suffix 원 vs prefix ₩). - Tabular numerals applied consistently. - Color semantics consistent (money-positive / money-negative / neutral). - Smaller payload than AmountInput (no input wiring).

Anatomy

Default:                  Negative (expense):           Hero (large display):
₩2,847,500                  -₩5,500                     ₩12,847,500
                                                          ↑ 12,500원 이번 달

Korean number format:    With sign explicit:           Foreign currency:
1,200만원                 +₩2,500,000                 $25.00 (약 ₩33,300)

API

<KRWAmount value={2847500} />
<KRWAmount value={-5500} type="expense" />
<KRWAmount value={user.balance} variant="hero" delta={{ value: 12500, period: "이번 달" }} />
<KRWAmount value={1200000} format="korean" />     // "1,200만원"
Prop Type Default Description
value number — Amount in won (smallest unit)
currency "KRW" (locked) "KRW" Reserved for future i18n
type "income" \| "expense" \| "transfer" \| "neutral" inferred from sign Drives color
variant "default" \| "compact" \| "hero" \| "inline" "default" Size + emphasis
format "comma" \| "korean" "comma" "1,200,000" vs "120만"
affixStyle "prefix" \| "suffix" "suffix" 1,200,000원 vs ₩1,200,000
showSign boolean false Force + for positive
precision number 0 Decimals (always 0 for KRW)
delta Delta — Below-amount comparison
compactThreshold number 10000 When format=korean: only convert above this

Variants

default

Standard inline display. Body-size text, tabular numerals.

<KRWAmount value={2847500} />
Renders: ₩2,847,500 or 2,847,500원 depending on convention.

compact

Smaller text, for table cells / sidebars.

<KRWAmount value={2847500} variant="compact" />

hero

Large display for hero amounts (account balance, total order): - Font: 32–48px - Weight: 700 - Tabular numerals - Optional delta below

<KRWAmount
  value={user.balance}
  variant="hero"
  delta={{ value: 12500, period: "이번 달", goalDirection: "up" }}
/>

Renders: 

₩12,847,500
↑ 12,500원 이번 달

inline

Minimal styling — fits inside a sentence:

<p>총 결제 금액은 <KRWAmount value={45000} variant="inline" />입니다.</p>

Format styles

comma (default)

Standard thousands separator: 2,847,500원 or ₩2,847,500.

korean

Korean number names (만, 억) for compact display: - < 10,000 won: 123원 - 10,000–9,999,999 won: 1,234만원 (showing 만 as the unit) - ≥ 10,000,000 won: 1억 2,345만원

Use korean format for: - Real estate prices (massive amounts) - Investment account totals - Hero displays in casual consumer apps

Don't use for transactional amounts (cart totals, transfers) — full digits required for accuracy.

Type / color mapping

Per knowledge/patterns/money-and-amount.md:

type Color Sign default
expense --color-money-negative -
income --color-money-positive + (if showSign)
transfer --color-money-neutral - or none
neutral --color-text-primary none

Inferred from sign by default; override with type prop.

Tokens consumed

--color-text-primary
--color-money-positive
--color-money-negative
--color-money-neutral
--font-feature-amount: 'tnum' 1   (critical)
--font-size-sm, --font-size-base, --font-size-2xl, --font-size-4xl
--font-weight-semibold, --font-weight-bold

Accessibility

  • Render as <span> with semantic-aware aria-label: 
    <span aria-label="290만 원">₩2,847,500</span>
  • For type="expense": aria-label="5,500원 지출".
  • For income: aria-label="2,500,000원 수입".
  • Color is supplementary; don't encode meaning by color alone — sign + label do the work for screen readers.

Code examples

// Transaction list cell
<KRWAmount value={tx.amount} type={tx.type} variant="compact" />

// Account balance hero
<KRWAmount
  value={account.balance}
  variant="hero"
  delta={{
    value: account.monthlyChange,
    period: "이번 달",
    goalDirection: account.balanceType === "savings" ? "up" : undefined,
  }}
/>

// Receipt total
<KRWAmount value={order.total} variant="default" affixStyle="prefix" />

// Inline in narrative
<p>이번 달 지출: <KRWAmount value={monthlyExpense} type="expense" variant="inline" /></p>

// Korean compact for property listing
<KRWAmount value={propertyPrice} format="korean" variant="hero" />
{/* Renders: 5억 2,000만원 */}

// Foreign equivalent
<div>
  <span>$25.00</span>
  <span className="text-text-secondary">
    (약 <KRWAmount value={33300} variant="inline" />)
  </span>
</div>

Edge cases

  • Zero: render as 0원 or ₩0 (not -원).
  • Negative amount with showSign: prefer -₩5,500 not ₩-5,500.
  • Very large (조 level): always full digits or with 조 unit. Don't crash.
  • Floating-point error in input: round to integer at the boundary (Math.round(value)).
  • Currency conversion display: pair with KRWAmount for the Korean half + native span for the foreign currency.

Don't

  • Don't show decimals for KRW. Round to integer at compute.
  • Don't omit tabular numerals. Tables with mixed widths look broken.
  • Don't auto-convert to korean format for transactional values — accuracy matters.
  • Don't forget signed-amount color logic — silently positive amounts colored as negative is a real bug.
  • Don't use --color-error for expense color. money-negative is its own axis.

API rationale

  • value is a number, not a formatted string: source of truth. KRWAmount is the single point of formatting.
  • type separate from sign: a positive transfer (e.g., +₩100,000 to your savings account) is "neutral", not "income".
  • format opt-in for Korean compact: full digits is the safer default; korean is the display option.

Cross-reference