envus

envus

A zero-dependency environment configuration and validation library for Node.js. It provides a clear and explicit schema-based API for reading and validating environment variables, with support for nested config objects, default values, strict mode, and optional .env loading.

Features

API Reference

loadEnv(options?)

Lightweight .env loader.

loadEnv({
  path?: string;        // default: '.env'
  override?: boolean;   // default: false
  ignoreMissing?: boolean; // default: true
  forgiving?: boolean;  // default: true
  encoding?: BufferEncoding;
});

defineConfig(tree, options?)

Validates environment variables and returns a fully typed config object.

defineConfig(tree, {
  strict?: boolean;        // reject unknown env vars
  source?: Record<string, string | undefined>; // custom env source
  formatError?: (issues) => Error; // custom error formatter
});

schema(key)

Creates a schema builder for the given environment variable.

schema("NAME").string();
schema("PORT").number();
schema("DEBUG").boolean();
schema("MODE").enum(["dev", "prod"]);
schema("LIST").array();
schema("JSON").json();
schema("CUSTOM").custom(fn);

Common Modifiers

.required()
.optional()
.default(value)
.description(text)

Type-Specific Modifiers

String

.minLength(n)
.maxLength(n)
.pattern(regex)
.trim()

Number

.min(n)
.max(n)
.int()
.positive()
.negative()

Array

.of(schema("X").number())

Errors

EnvValidationError contains all collected validation errors.

try {
  defineConfig(...);
} catch (err) {
  console.error(err.issues);
}

• Zero runtime dependencies
• Explicit and type-friendly schema API
• Nested configuration trees
• Required, optional, defaulted, and constrained values
• Lightweight .env loader (optional)
• Works with both CommonJS and ESM
• Strict mode to block unknown env vars

Installation

npm install envus

Basic Usage

import { loadEnv, defineConfig, schema } from "envus";

loadEnv(); // optional

const config = defineConfig({
  app: {
    name: "MyService",
    port: schema("PORT").number().min(1000).max(9999).default(3000),
    debug: schema("DEBUG").boolean().default(false),
  },
  security: {
    apiKey: schema("API_KEY").string().minLength(10).required(),
  },
  cache: {
    ttl: schema("CACHE_TTL").number().positive().default(3600),
  },
  features: {
    admins: schema("ADMINS").array().default(["root"]),
  }
});
```ts
import { loadEnv, defineConfig, schema } from "envus";

// Optional: load .env file
loadEnv();

const config = defineConfig({
  app: {
    name: "MyService",
    port: schema("PORT").number().default(3000),
  },
  db: {
    url: schema("DB_URL").string().required(),
    pool: schema("DB_POOL").number().default(5),
  }
});

console.log(config.app.port);

Schema Types

schema("KEY").string();
schema("KEY").number();
schema("KEY").boolean();
schema("KEY").enum(["dev", "prod"]);
schema("KEY").array();
schema("KEY").json();
schema("KEY").custom(raw => parseInt(raw || "0"));

Constraints

.required()
.optional()
.default(value)
.description(text)

Strict Mode

const config = defineConfig(schemaTree, {
  strict: true  // throws if extra env vars are present
});

Loading .env Files

loadEnv({ path: ".env.local", override: false });

Works alongside external dotenv loaders:

import "dotenv/config";

Error Handling

Errors are aggregated and thrown as EnvValidationError.

try {
  defineConfig({...});
} catch (err) {
  console.error(err);
}

Migration from v1

envus v2.0.0 is a complete rewrite of the library. The old API:

• validateEnv()
• resolveEnv()

has been removed, as the new schema-based system provides a more robust and type-safe configuration workflow.

If you rely on the old behavior, you can install the legacy version:

npm install envus@1.0.0-a

What's New in v2

• Explicit schema builder using schema("KEY")
• Rich chaining API for validation (min, max, patterns, positive, etc.)
• Nested config trees with defineConfig()
• Optional .env loader with loadEnv()
• Strong TypeScript inference
• Strict mode for detecting unknown environment values
• Zero runtime dependencies
• More predictable and extensible architecture

License

MIT