SOURCE

function assert(value,text) {
  if(value === true) {
    console.log(text)
  } else {
    console.log('error')
  }
}
function Person(){}
function Ninja(){}

Ninja.prototype = new Person()

const ninja = new Ninja()

assert(ninja instanceof Ninja,"our ninja is a Ninja")
assert(ninja instanceof Person,"a ninja is also a person")