Benchmarking Array.prototype.indexOf and Object in operator

.gitignore

node_modules/

README.md

$ node --version
v0.12.6
$ node index.js
Array: indexOf x 876,895 ops/sec ±0.95% (95 runs sampled)
Object with prototype: in operator x 18,518,152 ops/sec ±0.84% (94 runs sampled)
Object with prototype: value not undefined x 85,706,356 ops/sec ±0.75% (95 runs sampled)
Object with prototype: typeof value not undefined x 84,955,696 ops/sec ±0.95% (94 runs sampled)
Object without prototype: in operator x 18,283,395 ops/sec ±0.83% (93 runs sampled)
Object without prototype: value not undefined x 83,992,518 ops/sec ±1.43% (91 runs sampled)
Object without prototype: typeof value not undefined x 84,716,082 ops/sec ±0.80% (94 runs sampled)
Fastest is Object with prototype: value not undefined,Object with prototype: typeof value not undefined

index.js

'use strict';

var assert = require('assert');
var benchmark = require('benchmark');

var suite = new benchmark.Suite();
var array = Array.apply(null, {length: 10000}).map(Number.call, Number);
var objectWithPrototype = array.reduce(function(acc, element) { acc[element] = null; return acc; }, {});
var objectWithoutPrototype = array.reduce(function(acc, element) { acc[element] = null; return acc; }, Object.create(null));

suite.add('Array: indexOf', function() {
  assert(array.indexOf(999) > -1);
});

suite.add('Object with prototype: in operator', function() {
  assert('999' in objectWithPrototype);
});

suite.add('Object with prototype: value not undefined', function() {
  assert(objectWithPrototype['999'] !== undefined);
});

suite.add('Object with prototype: typeof value not undefined', function() {
  assert(typeof objectWithPrototype['999'] !== 'undefined');
});

suite.add('Object without prototype: in operator', function() {
  assert('999' in objectWithoutPrototype);
});

suite.add('Object without prototype: value not undefined', function() {
  assert(objectWithoutPrototype['999'] !== undefined);
});

suite.add('Object without prototype: typeof value not undefined', function() {
  assert(typeof objectWithoutPrototype['999'] !== 'undefined');
});

suite
  .on('cycle', function(event) { console.log(String(event.target)); })
  .on('complete', function() { console.log('Fastest is ' + this.filter('fastest').pluck('name')); })
  .run({ 'async': true });

package.json

{
  "dependencies": {
    "benchmark": "1.0.0"
  }
}