Best practice

Don't use global state like env variables in modules

28. December 2025

Don't use global state like env variables in modules, only on the very top-level or in one central location. Pass it in the constructor.

This hides dependencies to configuration values and makes them hard to spot.

Bad

class Foo {
  doSomething() {
    console.log(process.env.MY_ENV);
  }
}

new Foo().doSomething();

Good

class Foo {
  constructor(myEnv) {
    this.myEnv = myEnv;
  }
  doSomething() {
    console.log(this.myEnv);
  }
}

new Foo(process.env.MY_ENV).doSomething();