Simple environment variable validation with Zod

config.ts

import 'dotenv/config';
import { z } from 'zod';

/*
 * By default, the zod library will throw an error if the environment variable is missing.
 * All environment variables are string by default.
 * */
function zodEnvCheck(value: string) {
  return z.string({ message: `Environment variable missing: ${value}` }).parse(process.env[value]);
}

export const CONFIG = {
  LOG_LEVEL: zodEnvCheck('LOG_LEVEL'),
  ENVIRONMENT: zodEnvCheck('ENVIRONMENT'),
};

If an environment variable is missing, Zod will throw an error in this format

[email protected]/node_modules/zod/lib/types.js:55
[0]                 const error = new ZodError_1.ZodError(ctx.common.issues);
[0]                               ^
[0]
[0] ZodError: [
[0]   {
[0]     "code": "invalid_type",
[0]     "expected": "string",
[0]     "received": "undefined",
[0]     "path": [],
[0]     "message": "Environment variable missing: LOG_LEVEL"
[0]   }
[0] ]

so you know exactly which one is missing :)