mmntjs

library1.0.0jsnpmunverified

mmntjs v1.0.0 is a drop-in replacement for moment.js that provides a migration path to the Temporal API. It implements the full moment.js API surface and allows gradual migration file-by-file without breaking existing code. Ships TypeScript types, supports Node >=16. Key differentiators: zero-code alias using npm alias (`moment@npm:mmntjs`), automated codemod (`npx mmntjs migrate`), coexistence mode with original moment.js, and multiple entry points including `lite` (14.8 KB gzip), `full` (45.1 KB), tree-shakeable `fns` (0.5-1.3 KB), and a `temporal` bridge. Includes 136 locales and optional timezone support via separate package `mmntjs-timezone`. Released with weekly cadence.

devops

npm install mmntjs

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · MMNTJS

mmntjs

devopsjavascriptv1.0.0

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

moment

✓ import moment from 'mmntjs'

✗ import { moment } from 'mmntjs'

mmntjs exports a default moment function, not a named export.

moment (alias via npm)

✓ npm install moment@npm:mmntjs \n import moment from 'moment'

✗ npm install mmntjs && import moment from 'moment' // still original moment

Use npm alias to replace moment.js without changing import statements.

mmntjs/fns

✓ import { format } from 'mmntjs/fns'

✗ import { format } from 'mmntjs' // wrong export location

Tree-shakeable functions are exported from 'mmntjs/fns', not from main package.

Demonstrates alias mode, gradual migration, lite with locale, and Temporal bridge.

// Option A: Zero-code alias // npm install moment@npm:mmntjs import moment from 'moment'; const now = moment(); console.log(now.format('YYYY-MM-DD')); // e.g. 2025-03-15 // Option C: Gradual migration // npm install mmntjs import fm from 'mmntjs'; const startOfMonth = fm('2025-03-15').startOf('month'); console.log(startOfMonth.format()); // 2025-03-01T00:00:00+00:00 // Using lite with locales import m from 'mmntjs/lite'; import 'mmntjs/plugin/format-parse'; import { jaLocale } from 'mmntjs/locale/ja'; m.locale('ja', jaLocale); console.log(m().format('LL')); // 2025年3月15日 // Temporal bridge import { toTemporal, fromTemporal } from 'mmntjs/temporal'; const t = toTemporal(m('2025-03-15')); console.log(t instanceof Temporal.PlainDate); // true

Debug

Known issues

gotchammntjs does not support mutable moment objects; mutations are applied immutably and return new instances.

fix

Use method chaining or assign results to new variables: `const m2 = m1.add(1, 'day');`

affects: >=1.0.0

deprecatedmoment().zone() is deprecated. Use moment().utcOffset() instead.

fix

Replace `.zone(value)` with `.utcOffset(value)`.

affects: >=1.0.0

gotchaLocale data may differ from moment.js for some regions. Verify locale-specific formatting.

fix

Test formatting strings with your target locales and report issues upstream.

affects: >=1.0.0

breakingIn v1.0.0, `moment.parseTwoDigitYear` is not supported. Use custom parsing if needed.

fix

Manually parse two-digit years before passing to moment.

affects: 1.0.0

gotchaThe `mmntjs/fns` entry point only exports functions, not a moment constructor.

fix

Use `import m from 'mmntjs'` for moment constructor, and `import { format } from 'mmntjs/fns'` for standalone functions.

affects: >=1.0.0

Errors

Common errors & fixes

Wrong import type: 'moment' is not exported from 'mmntjs'

Using named import instead of default import.

fix

Use `import moment from 'mmntjs'`

Cannot find module 'mmntjs/locale/ja' or its corresponding type declarations.

TypeScript not resolving locale imports; missing type declarations for subpath exports.

fix

Add `"moduleResolution": "bundler"` or `"node16"` in tsconfig.json.

moment is not a function

Importing 'mmntjs' in a non-ES module context and using require incorrectly.

fix

Use `import moment from 'mmntjs'` with ESM, or `const moment = require('mmntjs')` if CJS (but mmntjs is ESM-only).

Upgrade

Version history

1.0.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/yoshi-taka/mmntjs ↗

packagemmntjs ↗

homepagehttps://github.com/yoshi-taka/mmntjs#readme ↗