Run results for: Map keyed by Object

Comparing different methods for using an arbitrary object as a Map key, for a relatively small number of entries. Used to make decisions about how to cache WrappedEnum instances in ts-enum-util: https://github.com/UselessPickles/ts-enum-util

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36 OPR/107.0.0.0

Browser: Opera 107

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Benchmark engine: Benchmark.js

Native WeakMap by Object

2.2M/s

Native Map by Object

2.0M/s

Polyfill Map by Object

1.8M/s

Native Map by JSON

580K/s

Object by JSON

567K/s

View exact numbers

Test name	Executions per second
✓ Native WeakMap by Object	2,173,918 Ops/sec
Native Map by Object	2,049,569 Ops/sec
Polyfill Map by Object	1,799,202 Ops/sec
Native Map by JSON	580,147 Ops/sec
Object by JSON	566,743 Ops/sec

Script Preparation code:

function SlowMap() {
  this._keys = [];
  this._values = [];
}

SlowMap.prototype = {
  set: function(key, value) {
    const index = this._keys.indexOf(key);
    if (index !== -1) {
      this._values[index] = value;
    } else {
      this._keys.push(key);
      this._values.push(value);
    }
  },
  
  get: function(key) {
    const index = this._keys.indexOf(key);
    if (index !== -1) {
      return this._values[index];
    } else {
      return undefined;
    }
  }
};

var OBJECT_COUNT = 500;
var PROPERTY_COUNT = 10;
var OBJECTS = [];

var slowMapByObj = new SlowMap();
var nativeMapByObj = new Map();
var nativeWeakMapByObj = new WeakMap();
var nativeMapByJson = new Map();
var objectMapByJson = {};

for (let i = 0; i < OBJECT_COUNT; ++i) {
  var obj = {};
  
  for (let j = 0; j < PROPERTY_COUNT; ++j) {
    obj[i + "|" + j] = i * PROPERTY_COUNT + j;
  }
  
  OBJECTS.push(obj);
  slowMapByObj.set(obj, i);
  nativeMapByObj.set(obj, i);
  nativeWeakMapByObj.set(obj, i);
  nativeMapByJson.set(JSON.stringify(obj), i);
  objectMapByJson[JSON.stringify(obj)] = i;
}

var testLoopCount = 0;

Tests:

Polyfill Map by Object
var result = slowMapByObj.get(OBJECTS[testLoopCount++ % OBJECT_COUNT]);
Native Map by Object
var result = nativeMapByObj.get(OBJECTS[testLoopCount++ % OBJECT_COUNT]);
Native Map by JSON
var result = nativeMapByJson.get(JSON.stringify(OBJECTS[testLoopCount++ % OBJECT_COUNT]));
Object by JSON
var result = objectMapByJson[JSON.stringify(OBJECTS[testLoopCount++ % OBJECT_COUNT])];
Native WeakMap by Object
var result = nativeWeakMapByObj.get(OBJECTS[testLoopCount++ % OBJECT_COUNT]);