Monomorphic vs Polymorphic function

mono-vs-poly.js

const {Benchmark} = require('benchmark');
var suite = new Benchmark.Suite;

function monomorphic (person) {
  const array = [];

  for (let i = 10; i--; ) {
    array.push(person.age * i);
  }

  if (array[0] % 2) {
    return array.map(e => e + 42);
  }
  return array.map(e => e + 21);
}

function polymorphic (person) {
  const array = [];

  for (let i = 10; i--; ) {
    array.push(person.age * i);
  }

  if (array[0] % 2) {
    return array.map(e => e + 42);
  }
  return array.map(e => e + 21);
}


let ret;
// add tests
suite
.add('monomorphic function', function() {
  ret = monomorphic({ age: 21, name: 'Aschen' });
  ret = monomorphic({ age: 29, name: 'Aschen' });
})
.add('polymorphic function', function() {
  ret = polymorphic({ age: 21, name: 'Aschen' });
  ret = polymorphic({ name: 'Aschen', age: 29 });
})
// add listeners
.on('cycle', function(event) {
  console.log(String(event.target));
})
.on('complete', function() {
  console.log('Fastest is ' + this.filter('fastest').map('name'));
})
// run async
.run();

/*

$ node node/mono-vs-poly.js 
 monomorphic function x 3,975,995 ops/sec ±2.50% (86 runs sampled)
 polymorphic function x 2,111,454 ops/sec ±0.38% (91 runs sampled)
Fastest is monomorphic function

*/