JavaScript V8 inline cache behavior differences

ic_behavior.js

main()

function main() {
  monomorphic()
  polymorphic()
  megamorphic()
}


function bench(label, people) {
  const ITERATIONS = 1000 * 1000 * 1000;
  console.time(label)

  for (var i = 0; i < ITERATIONS; i++) {
    people[i & 7].lastname
  }

  console.timeEnd(label);
}


function monomorphic() {
// monomorphic
  const han = {firstname: "Han", lastname: "Solo"}
  const luke = {firstname: "Luke", lastname: "Skywalker"}
  const leia = {firstname: "Leia", lastname: "Organa"}
  const obi = {firstname: "Obi", lastname: "Wan"}
  const yoda = {firstname: "", lastname: "Yoda"}
  const people = [han, luke, leia, obi, yoda, luke, leia, obi]

  bench("monomorphic", people)
}

function polymorphic() {
  const han = {firstname: "Han", lastname: "Solo", gender: "male"}
  const luke = {firstname: "Luke", lastname: "Skywalker", job: "Jedi"}
  const leia = {firstname: "Leia", lastname: "Organa", gender: "female"}
  const obi = {firstname: "Obi", lastname: "Wan"}
  const yoda = {lastname: "Yoda"}
  const people = [han, luke, leia, obi, yoda, luke, leia, obi]

  bench("polymorphic", people)
}


function megamorphic() {
  const han = {firstname: "Han", lastname: "Solo", spacecraft: "Falcon"}
  const luke = {firstname: "Luke", lastname: "Skywalker", job: "Jedi"}
  const leia = {firstname: "Leia", lastname: "Organa", gender: "female"}
  const obi = {firstname: "Obi", lastname: "Wan", retired: true}
  const yoda = {lastname: "Yoda"}
  const people = [han, luke, leia, obi, yoda, luke, leia, obi]

  bench("megamorphic", people)
}