How to sanely make private variables in modern JavaScript

its2019AndWeCanFinallyDoPrivateVariables.js

// Using the WeakMap approach, the variables are kept outside of public access and when the instance of
// SomeClass is no longer referenced, all of its variables will be GCed as well

const instances = new WeakMap()

class SomeClass {
  constructor (privateVar1, privateVar2, privateVar3) {
    instances.set(this, {
      privateVar1,
      privateVar2,
      privateVar3
    })
  }

  someMethod () {
    const { privateVar1, privateVar2, privateVar3 } = instances.get(this)
    // Do stuff with the private variables, make sure you instances.set any changes you need to make
  }
}