numkey

Open source by DevsLab

English | 한국어 · 📺 Live demo

Try it online: ⚡ StackBlitz — Vanilla · Vue · React · Svelte · Solid | 📦 CodeSandbox

"It's a string, but it's a number." Every business app has these fields — amounts, quantities, prices — and every team rebuilds the same input by hand: live thousands grouping (10,000), no leading zeros, right-aligned, numeric keypad on mobile, and a caret that doesn't jump while separators appear and disappear around it.

numkey is that input, done once:

• Caret-safe live formatting — type into the middle of 1,234,567 and the cursor stays where you expect, even as groups reflow
• String-first value model — the canonical value is a plain numeric string ("1234567.89"), never an IEEE 754 float, so money is safe
• Leading-zero cleanup (007 → 7), full-width digit normalization (１２３ → 123 — Korean/Japanese IME), paste sanitizing (₩ 1,234원 → 1234)
• Right alignment + inputmode set automatically (opt-out available)
• IME-safe — nothing runs mid-composition
• Zero dependencies, TypeScript-first, ESM/CJS dual + a CDN global build
• Works with plain <script> (JSP/PHP/anything server-rendered), Vue 3, and React

Wrong-keyboard-layout text in the same form? That's numkey's sibling, kokey.

One script tag; everything else is markup. Inputs are auto-bound, including ones added to the DOM later.

<script src="https://cdn.jsdelivr.net/npm/@devslab/numkey"></script>

<input data-numkey>                            <!-- integers: 1,234,567 -->
<input data-numkey="2">                        <!-- 2 decimals: 1,234.56 -->
<input data-numkey data-numkey-negative>       <!-- minus allowed -->
<input data-numkey data-numkey-align="left">   <!-- keep left alignment -->

Server-rendered values (<input data-numkey value="1234567">) are formatted on load. To read the raw value back before submitting:

<script>
  const raw = numkey.getValue(document.querySelector('#amount')) // "1234567"
</script>

(Or simply strip separators server-side — the posted value is the display value.)

data-numkey is the on-switch. It is what gets an input bound (auto-init watches input[data-numkey]), and its value doubles as the max decimal places — empty means integers only. Every other data-numkey-* attribute is an option that is only read from inputs that have data-numkey; on its own it does nothing:

<input data-numkey>                        <!-- ON, integers: 1,234,567 -->
<input data-numkey="2">                    <!-- ON, 2 decimals: 1,234.56 -->
<input data-numkey="2" data-numkey-negative>  <!-- options stack -->
<input data-numkey-locale="auto">          <!-- ✗ does NOTHING — no data-numkey -->
<input>                                    <!-- plain input, untouched -->

By default the display is deterministic: every visitor sees 1,234,567.89, whatever their browser is set to — which is what business forms usually need. data-numkey-locale opts a field into locale separators:

<!-- everyone sees 1,234,567.89 — the default, no locale involved -->
<input data-numkey="2">

<!-- follows the visitor's browser language:
     a German browser shows  1.234.567,89
     a Korean browser shows  1,234,567.89 -->
<input data-numkey="2" data-numkey-locale="auto">

<!-- pinned to German formatting for every visitor -->
<input data-numkey="2" data-numkey-locale="de-DE">

The locale changes only how the value is drawn. The canonical value is always "1234567.89" — numkey.getValue(el) returns the same string in all three cases. Since a plain form POST submits the display value, a form using locales should post through data-numkey-name (below) or normalize server-side.

The Indian system groups the last three digits and then every two — 12,34,56,789, not 123,456,789. Give group a [primary, secondary] pair, or just name the locale:

<input data-numkey data-numkey-group="3,2">      <!-- 1,00,000 (1 lakh) -->
<input data-numkey data-numkey-locale="en-IN">   <!-- same, derived -->

format('10000000', { group: [3, 2] })   // '1,00,00,000'  (1 crore)
format('123456789', { locale: 'en-IN' }) // '12,34,56,789'

An explicit group always wins over the locale, and a single number stays uniform grouping (4 → 1234,5678 for 만-style). group: 0 turns separators off entirely.

The "150만" hint that banking and fintech UIs render next to amount fields — usually rebuilt by hand in every project:

<input data-numkey data-numkey-korean>
<!-- typing 1500000 renders:
     <input value="1,500,000"> <span class="numkey-korean">150만</span> -->

<input data-numkey data-numkey-korean="#my-hint">  <!-- use your own element -->

An empty attribute generates a <span class="numkey-korean"> right after the input (unstyled — add "원" with CSS .numkey-korean::after { content: " 원" }); a value is treated as a CSS selector for an existing element. The same engine is available as a pure function:

import { toKorean } from '@devslab/numkey'

toKorean('1500000')      // "150만"
toKorean('927483041001') // "9,274억 8,304만 1,001"
toKorean('100000001')    // "1억 1" — zero groups omitted

And the inverse — accept the shorthand people actually type into 부동산/주식 apps, either as a pure function or on the field itself:

import { fromKorean } from '@devslab/numkey'

fromKorean('3만5천')   // "35000"
fromKorean('1.5억')    // "150000000"
fromKorean('삼십오만')  // "350000"

<input data-numkey data-numkey-korean-entry>
<!-- typing 3만5천 is left alone (no live reformat fighting the IME);
     blur converts it to 35,000 -->

getValue and the data-numkey-name hidden sync (below) see the parsed value even while the draft is still on screen.

A plain form POST submits what the field displays — 1,234,567 — which every server handler then has to de-comma. data-numkey-name generates a hidden input that always carries the settled canonical value instead:

<form method="post">
  <!-- the visible input has NO name; the hidden one posts amount=1234567 -->
  <input data-numkey data-numkey-name="amount" value="1234567">
</form>

The hidden value is kept settled even mid-typing (1,234. posts 1234), so whatever moment the form submits, the server sees a clean number.

Use type="text" inputs. numkey sets inputmode so mobile keyboards show the numeric keypad; type="number" has no caret API and fights formatting.

npm install @devslab/numkey

import { format, parse, bind, observe } from '@devslab/numkey'

format('1234567.5', { decimals: 2 })   // "1,234,567.5"
parse('₩ 1,234,567원')                  // "1234567"

bind(document.querySelector('#amount'), { decimals: 2 }) // one element
observe()                                                // all [data-numkey]

<script setup>
import { ref } from 'vue'
import { NumkeyInput, vNumkey } from '@devslab/numkey/vue'

const amount = ref('') // always canonical: "1234567"
</script>

<template>
  <!-- v-model gets the canonical value; the field shows 1,234,567 -->
  <NumkeyInput v-model="amount" :decimals="2" negative />

  <!-- or the directive for plain inputs -->
  <input v-numkey="2">
</template>

import { NumkeyInput, useNumkey } from '@devslab/numkey/react'

// Controlled: value/onValueChange speak canonical strings
const [amount, setAmount] = useState('')
<NumkeyInput value={amount} onValueChange={setAmount} decimals={2} negative />

// Uncontrolled: ref-callback hook
<input ref={useNumkey({ decimals: 2 })} defaultValue="1234567" />

An action — and it imports nothing from svelte, so there is no peer dependency at all. bind:value works: the action re-syncs the binding after formatting, so the bound variable holds the display value. For the canonical value use onValue.

<script>
  import { numkey } from '@devslab/numkey/svelte'
  let amount = ''   // canonical: "1234567"
  let display = ''  // display:   "1,234,567"
</script>

<input use:numkey={{ decimals: 2, onValue: (v) => (amount = v) }} />
<input use:numkey={2} bind:value={display} />
<input use:numkey />                      <!-- options from data-numkey* -->

A use: directive (reactive to a signal) and a ref factory. Solid delegates input at the document level, so onInput already reads the formatted value — no re-sync needed.

import { numkey, useNumkey } from '@devslab/numkey/solid'

const [amount, setAmount] = createSignal('') // canonical
<input use:numkey={{ decimals: 2, onValue: setAmount }} />
<input ref={useNumkey({ decimals: 2 })} value="1234567" />

• European formats work via options: { separator: '.', decimalPoint: ',' } displays 1.234.567,89 while the canonical value stays "1234567.89".
• Accounting negatives paste correctly: (1,234) — what Excel and most ERP exports produce — reads as -1234 on a negative field (currency signs may sit outside the parens). Parentheses that don't enclose digits, like (주)한국 1234, are left alone, and a positive-only field ignores the form entirely.
• Backspace/Delete next to a group separator deletes the adjacent digit in one keystroke (the separator is skipped, and the reformat handles the rest).

• v0.2 — Korean amount reading (150만) + hidden canonical sync ✅ shipped
• v0.3 — Korean shorthand entry (3만5천 → 35,000) ✅ shipped
• v0.4 — smart deletion across separators + min/max ✅ shipped
• v0.5 — Svelte action / Solid directive ✅ shipped
• v0.6 — Indian lakh/crore grouping (12,34,567) + locale-derived group sizes ✅ shipped

Nothing else is planned — open an issue if your form needs something this doesn't do.

Ideas we considered and why they are not here (in-field prefix/suffix, the unspecified Korean reading of negatives): docs/backlog.md.

Issues and PRs welcome — see CONTRIBUTING.md for the dev setup and the ground rules (string-first values, IME safety, char-by-char regression tests).

• kokey — the keyboard-layout sibling in the "-key" input family: wrong-layout text restoration with a full Korean IME automaton
• More open source from devslab

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