Working with Environment Variables

node --env-file=.env --env-file=.env.local app.js

// Must load BEFORE other imports that read process.env
import "dotenv/config";
import express from "express";
// Or with options
import dotenv from "dotenv";
dotenv.config({ path: ".env.production", override: false });

NODE_ENV=development
PORT=3000
DATABASE_URL=postgres://user:pass@localhost:5432/app
JWT_SECRET="multi word secret"
ALLOWED_ORIGINS=https://app.example.com,https://admin.example.com
# Comments allowed
LOG_LEVEL=info

const port = Number(process.env.PORT) || 3000;
const host = process.env.HOST ?? "0.0.0.0";  // ?? respects empty string
const debug = process.env.DEBUG === "true";
const origins = (process.env.ALLOWED_ORIGINS || "").split(",").filter(Boolean);

import { z } from "zod";

const envSchema = z.object({
  NODE_ENV: z.enum(["development", "production", "test"]),
  PORT: z.coerce.number().int().positive().default(3000),
  DATABASE_URL: z.string().url(),
  JWT_SECRET: z.string().min(32)
});

export const env = envSchema.parse(process.env);  // throws on invalid

.env
.env.local
.env.*.local
# Track template / example
!.env.example

import env from "env-var";

export const config = {
  port: env.get("PORT").default(3000).asPortNumber(),
  dbUrl: env.get("DATABASE_URL").required().asUrlString(),
  origins: env.get("ALLOWED_ORIGINS").required().asArray(","),
  logLevel: env.get("LOG_LEVEL").default("info").asEnum(["debug","info","warn","error"])
};

# package.json scripts (cross-env for Windows compatibility)
"start": "cross-env NODE_ENV=production node app.js"
# Or natively in shell
NODE_ENV=production node app.js
# PM2
pm2 start app.js --env production