this is evil

this-is-evil.mjs

export class Foo {
  constructor(name) {
    this.name = name
  }
   DoIt() {
    console.log(`Hello ${this.name}`);
  }
}

const f = new Foo("Direct");

// works directly
f.DoIt()

// works in an arrow function because it's in a closure
// this is generally what you want to do
f.name = 'Closure'
const callbackLambda = () => f.DoIt()
callbackLambda();

// here we are getting the function, but we are explicitly binding it to an instance
f.name = 'Bound'
const callbackBound = f.DoIt.bind(f);
callbackBound();

try {
  // here we are getting the function and not the method on our instance f
  f.name = 'Function'
  const callbackDirect = f.DoIt;
  // goes boom
  callbackDirect();
} catch (err) {
  console.error('It went boom', err)
}