prototype-inheritance.js

'use strict'

function F1() {
  console.log('construct F1')
  this.name = 'F1'
  this.f1 = true
}

// does not call the constructor of F1, works with instanceof
function F2() {
  console.log('construct F2')
  this.name = 'F2'
  this.f2 = true
}
F2.prototype = F1.prototype

// calls the constructor of F1, does not work with instanceof
function F3() {
  console.log('construct F3')
  F1.call(this)
  this.name = 'F3'
  this.f3 = true
}

// calls the constructor of F1, works with instanceof, introduces an additional prototype "layer"
function F4() {
  console.log('construct F4')
  Object.setPrototypeOf(this, new F1())
  this.name = 'F4'
  this.f4 = true
}

// calls the constructor of F1, works with instanceof, does not introduce an additional prototype "layer"
function F5() {
  console.log('construct F5')
  F1.call(this)
  this.name = 'F5'
  this.f5 = true
}
F5.prototype = F1.prototype

for (const F of [F1, F2, F3, F4, F5]) {
  console.log(F)
  const f = new F
  console.log('  name=%s', f.name)
  console.log('  instanceof F1=%s', f instanceof F1)
  console.log('  prototype === F1.prototype = %s', Object.getPrototypeOf(f) === F1.prototype)
  console.log()
}