ascertain

library3.2.44jsnpmunverified

Zero-dependency JavaScript schema validator that compiles native JS values into fast validator functions. Current stable version is 3.2.44. Released regularly (multiple versions per month). Key differentiators: faster than AJV and dramatically faster than Zod for all-errors validation, JavaScript-native schemas (constructors, literals, arrays, objects), compiled validators with first-error and all-errors modes, full TypeScript support with type inference, zero dependencies, and support for Standard Schema v1 for interoperability with tRPC and TanStack Form.

testing

npm install ascertain

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · ASCERTAIN

ascertain

testingjavascriptv3.2.44

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.

compile

✓ import { compile } from 'ascertain'

✗ const { compile } = require('ascertain')

ESM-only; CommonJS require() works but is discouraged. TypeScript types included.

ascertain

✓ import ascertain from 'ascertain'

✗ import { ascertain } from 'ascertain'

Default export for convenience wrapper that compiles and throws on failure.

optional

✓ import { optional } from 'ascertain'

✗ import optional from 'ascertain'

Named export from the package root.

Demonstrates compiled validation with discriminated unions, optional fields, and union literals.

import { compile, discriminated, optional, or } from 'ascertain'; const schema = { id: Number, role: or('admin', 'user', 'guest'), score: optional(Number), notifications: [ discriminated( [ { type: 'email', address: String }, { type: 'sms', phone: String }, { type: 'push', token: String }, ], 'type', ), ], }; const validateUser = compile(schema); const userData = { id: 1, role: 'admin', notifications: [{ type: 'email', address: 'test@example.com' }], }; if (!validateUser(userData)) { console.error(validateUser.issues); } else { console.log('Valid!'); }

Debug

Known issues

breakingIn version 3.x, compile() returns a validator object with an issues property instead of throwing directly.

fix

Check validateUser.issues for errors instead of catching thrown exceptions.

affects: >=3.0.0

deprecatedThe ascertain() convenience function is deprecated in favor of compile() for repeated use.

fix

Use compile() for reusable validators; ascertain() for one-off throws.

affects: >=2.0.0

gotchaWhen using discriminated(), the discriminator field must be present in every variant and must be a string key.

fix

Ensure all discriminated variants include the discriminator field as a string literal.

affects: *

Errors

Common errors & fixes

Error: Cannot find module 'ascertain'

Package not installed or running in environment without ESM support.

fix

Run 'npm install ascertain' and use import syntax; ensure Node.js version >=12 or use bundler.

TypeError: compile is not a function

Default import used for named export; import { compile } from 'ascertain' required.

fix

Change to 'import { compile } from 'ascertain'.

TypeError: validateUser.issues is undefined

Using compile() in version 2.x where return was boolean; version 3.x returns object with issues.

fix

Update to ascertain@3 and access validateUser.issues for error details.

Upgrade

Version history

3.2.44latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

23 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/3axap4eHko/ascertain ↗

packageascertain ↗

homepagehttps://github.com/3axap4eHko/ascertain#readme ↗