valcheckerRuntime-first validation with zero guesswork

Type-aligned initial schemas, state-aware fluent validation, tree-shakable plugins, and deterministic structured issues.

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🔗

State-Aware Fluent API

Initial schemas use nouns, validations use `isXxx`, and concrete transforms use `toXxx`, so editor autocomplete exposes only meaningful next steps.

🎯

TypeScript-Aligned Primitives

Primitive schemas mirror TypeScript identities. Runtime constraints such as finite numbers remain explicit, composable validation steps.

📋

Deterministic Issue Reporting

Validation failures produce structured issues with codes, payloads, and deep paths rather than throwing validation exceptions.

🌳

Tree-Shakable by Design

Use the default all-steps instance or build a custom instance from selected plugins while keeping the same fluent API.

⚡

Sync and Maybe-Async Pipelines

Direct values, promises, and thenables preserve execution order and the pipeline's actual completion mode.

🔧

Explicit Normalization

Loose primitives normalize TypeScript-compatible string representations without falling back to unrestricted JavaScript coercion.

See It In Action

The method name identifies the step's role, while the available methods narrow as the pipeline output changes.

import type { InferOutput } from 'valchecker'
import { v } from 'valchecker'

const UserSchema = v.object({
	name: v.string()
		.toTrimmed()
		.isNotEmpty(),
	email: v.string()
		.toLowercase(),
	age: [v.looseNumber()
		.isFinite()
		.isInteger()
		.isAtLeast(0)],
	role: v.union([
		v.literal('admin'),
		v.literal('user'),
		v.literal('guest'),
	]),
})

type User = InferOutput<typeof UserSchema>

const result = await UserSchema.execute(input)

if (v.isSuccess(result)) {
	console.log(result.value)
}
else {
	console.log(result.issues)
}

Why Valchecker?

Valchecker treats runtime validation, output transformation, TypeScript inference, and bundle composition as one API design problem. Primitive initial steps mirror TypeScript types; additional runtime guarantees are explicit isXxx validations; concrete output changes are toXxx transformations. Generic check() and transform() remain available when a named step cannot express the requirement.

npm install valchecker

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