src/lib/load-env.ts

import { config } from "dotenv";
import { existsSync } from "fs";
import { join } from "path";

export const load = <T extends Record<string, string> = Record<string, string>>(
  root: string = process.cwd(),
): T => {
  const localEnv = join(root, ".env.local");
  const modeEnv = join(root, `.env.${process.env.NODE_ENV}`);
  const defaultEnv = join(root, ".env");
  return [localEnv, modeEnv, defaultEnv].reduce<T>((prev, path) => {
    const variables = !existsSync(path) ? {} : (config({ path }).parsed ?? {});
    Object.entries(variables).forEach(([key, value]) => {
      if (!Object.prototype.hasOwnProperty.call(prev, key))
        Object.assign(prev, { [key]: value });
    });
    return prev;
  }, {} as T);
};

load();