Simple, TypeScript first, zero-dependency environment variable validation/initialization tool.

Why jet-env

• Small, quick, convenient zero-dependency.
• You can learn this tool in 5 minutes.
• Works client or server side.
• Automatically constructs environment-variable names from object keys.
• Sets up a completely type-safe object to hold all your environment variables.
• Includes 4 build-in validator-functions: (bool, num, date and str)
• transform() wrapper for validator-functions includes if a value needs to be modified first.
• Easier to learn and smaller han envalid.

Overview

This library does not load environment variables, but it provides a single function that will loop through an object and assignment an environment variable to each one. If the environment variable is undefined or the incorrect type, then an error will be thrown.

The environment variable name will be constructed using the keys on the object. PascalCase names will automatically be converted to UPPER_SNAKE_CASE. So if your environment variable is NODE_ENV then the key should be NodeEnv on the object key. This will work for nested objects tool. The parent-object's key name will be prepended to whatever the child-properties's key is.

If you want to override the behavior for naming the environment variables, you can pass an array instead of a function. The first value in the array must be a string and will be used to pull the environment variable (no prepending is done). The second value must be a validator-function

If you want your environment variable value transformed before validation, there is a helper function export that your can wrap your validator function with. There are also 4 default validator-functions (bool, num, date and str) that come packaged by default.

Notes on validators:

• An empty string will not satisfy the str function.
• date will convert any valid date value (string or number) to a Date object and make sure it's valid.
• For boolean types, there are several different variations which will satisfy the built-in bool function:
  • false/true, case doesn't matter
  • 0: false
  • 1: true
  • no: false case doesn't matter
  • yes: true case doesn't matter

Quick Glance

import jetEnv, { bool, date, num, transform } from 'jet-env';

const Env = jetEnv({
  NodeEnv: str, // NODE_ENV
  IsLocal: bool, // IS_LOCAL
  Port: num, // PORT
  BackEndUrl: str, // BACK_END_URL
  FrontEndUrl: str, // FRONT_ENV_URL
  BypassDbConn: transform(JSON.parse, (arg) => arg === true),
  S3BucketName: ['S3_BUCKET_NAME', str],
  S3BucketUrl: str, // S3_BUCKET_URL
  S3BucketExp: date, // S3_BUCKET_EXP
  Aws: {
    S3Credentials: {
      AccessKeyId: str, // AWS_S3_CREDENTIALS_ACCESS_KEY_ID
      SecretAccessKey: str, // AWS_S3_CREDENTIALS_SECRET_ACCESS_KEY 
    },
  },
});

Overriding Default Behavior

• The default behavior for formatting variable names, fetching values, and handling error messages can all be overridden by an optional options parameter as the second argument to jetEnv. Here's a overview of the options object:

{
  getValue?: (property: string, key?: string) => unknown; // Fetch the value, default is "=> process.env[property]"
  variableNameFormatter?: (name: string) => string; // Set your own custom function for formatting environment-variable names from object keys.
  onError?: (property: string) => void; // Change what happens when a validator-function fails (currently throws an error)
}

That's It!

Happy Coding :)