Benchmark: Object iteration vs Map iteration

Script Preparation code:

var obj = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
  e: 5,
  f: 6,
  g: 7,
  h: 8,
  i: 9,
  j: 10,
  k: 11,
  l: 12,
  m: 13,
  n: 14,
  o: 15,
  p: 16,
  q: 17,
  r: 18,
  s: 19,
  t: 20,
  u: 21,
  v: 22,
  w: 23,
  x: 24,
  y: 25,
  z: 26
};
var map = new Map(Object.entries(obj));

Tests:

Map - for of kv
let total = 0; for (const [key, value] of map) { total += value; }
Map - forEach
let total = 0; map.forEach(function(value, key) { total += value; });
Object.entries() - for of kv
let total = 0; for (const [key, value] of Object.entries(obj)) { total += value; }
Object.entries() - forEach
let total = 0; Object.entries(obj).forEach(function(value, key) { total += value; });
Object - for in
let total = 0; for (const key in obj) { total += obj[key]; }

Historical Performance Data aggregated from 128 community runs

Desktop Results:

Chrome 100 runs

Map - for of kv

6.9M/s

Map - forEach

4.2M/s

Object.entries() - for of kv

1.3M/s

Object - for in

707K/s

Object.entries() - forEach

251K/s

Fastest: Map - for of kv (27.5x faster)

View exact numbers

✓ Map - for of kv: 6,880,140 ops/sec
• Map - forEach: 4,224,913 ops/sec
• Object.entries() - for of kv: 1,271,885 ops/sec
• Object - for in: 706,525 ops/sec
• Object.entries() - forEach: 250,568 ops/sec

Firefox 19 runs

Object - for in

6.5M/s

Map - forEach

4.2M/s

Map - for of kv

1.6M/s

Object.entries() - for of kv

1.2M/s

Object.entries() - forEach

141K/s

Fastest: Object - for in (45.7x faster)

View exact numbers

✓ Object - for in: 6,469,104 ops/sec
• Map - forEach: 4,175,476 ops/sec
• Map - for of kv: 1,611,924 ops/sec
• Object.entries() - for of kv: 1,222,477 ops/sec
• Object.entries() - forEach: 141,455 ops/sec

Mobile Results:

Chrome 9 runs

Map - for of kv

3.0M/s

Map - forEach

1.7M/s

Object.entries() - for of kv

594K/s

Object - for in

343K/s

Object.entries() - forEach

102K/s

Fastest: Map - for of kv (29.5x faster)

View exact numbers

✓ Map - for of kv: 3,020,599 ops/sec
• Map - forEach: 1,738,110 ops/sec
• Object.entries() - for of kv: 593,839 ops/sec
• Object - for in: 342,902 ops/sec
• Object.entries() - forEach: 102,372 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map - for of kv
Map - forEach
Object.entries() - for of kv
Object.entries() - forEach
Object - for in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36

Browser/OS: Chrome 138 on Mac OS X 10.15.7

View result in a separate tab

Map - for of kv

11.1M/s

Object - for in

8.7M/s

Map - forEach

7.3M/s

Object.entries() - for of kv

2.0M/s

Object.entries() - forEach

354K/s

View exact numbers

Test name	Executions per second
✓ Map - for of kv	11,087,638 Ops/sec
Object - for in	8,745,834 Ops/sec
Map - forEach	7,329,178 Ops/sec
Object.entries() - for of kv	1,965,132 Ops/sec
Object.entries() - forEach	353,826 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

I'll break down the benchmark and explain what's being tested, compared options, pros/cons, and other considerations.

**Benchmark Definition**

The provided JSON represents a JavaScript microbenchmark that compares the performance of iterating over an object using different methods:

1. `for...of` with `Map` objects
2. `forEach` with `Map` objects
3. `for...of` with `Object.entries`
4. `forEach` with `Object.entries`
5. `for...in` with objects

**Script Preparation Code**

The script preparation code creates an object `obj` with 26 properties and a corresponding `Map` object `map` by converting the object's entries to a map using `Object.entries(obj)`. This sets up the test environment for each benchmark.

**Html Preparation Code**

There is no HTML preparation code provided, which suggests that the tests are performed in a JavaScript-only environment.

**Individual Test Cases**

Each test case has a unique benchmark definition and name. Here's a brief explanation of what each test case does:

1. **Map - for of kv**: Iterates over the `map` object using `for...of`.
2. **Map - forEach**: Iterates over the `map` object using `forEach`.
3. **Object.entries() - for of kv**: Iterates over the entries of the `obj` object using `for...of`, which is achieved by calling `Object.entries(obj)`.
4. **Object.entries() - forEach**: Iterates over the entries of the `obj` object using `forEach`.
5. **Object - for in**: Iterates over the properties of the `obj` object using `for...in`.

**Comparison Options**

The benchmark compares the performance of these five iteration methods:

* `Map` objects with `for...of` and `forEach`
* Objects with `Object.entries()` and `for...of`, as well as `Object.entries()` and `forEach`

**Pros and Cons**

Here are some general pros and cons for each iteration method:

* **`for...of` with `Map` objects**: Pros: Fast, efficient, and easy to use. Cons: May not work well with large maps or complex data structures.
* **`forEach` with `Map` objects**: Pros: Similar performance to `for...of`. Cons: Less intuitive than `for...of`.
* **`for...of` with `Object.entries`**: Pros: Easy to use and fast. Cons: May not work well with large objects or complex data structures.
* **`forEach` with `Object.entries`**: Pros: Similar performance to `for...of`. Cons: Less intuitive than `for...of`.
* **`for...in` with objects**: Pros: Fast, but may not be as efficient as other methods for iterating over object properties. Cons: May iterate over inherited properties or properties in a different order.

**Other Considerations**

* When working with large data structures, the performance of iteration methods can vary depending on the JavaScript engine and browser being used.
* `Map` objects are generally faster than arrays when it comes to iteration, but may have slower startup times due to the overhead of creating a map.
* The choice of iteration method depends on the specific use case and personal preference.

**Alternatives**

Some alternative iteration methods that are not included in this benchmark include:

* Using `array.prototype.forEach()` or other array methods
* Using `WeakMap` objects instead of regular maps
* Using `TypedArray` objects for fast iteration over numeric data

Keep in mind that the performance characteristics of these alternatives may vary depending on the specific use case and JavaScript engine being used.

Object iteration vs Map iteration (version: 0)

Comparing performance of: `Map - for of kv vs Map - forEach vs Object.entries() - for of kv vs Object.entries() - forEach vs Object - for in`

Created: 5 years ago by: Guest

Go to the latest result

Map - for of kv

Map - forEach

Object.entries() - for of kv

Object.entries() - forEach

Object - for in

Historical Performance Data aggregated from 128 community runs

Desktop Results:

Chrome 100 runs

Firefox 19 runs

Mobile Results:

Chrome 9 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Object iteration vs Map iteration (version: 0)

Comparing performance of: Map - for of kv vs Map - forEach vs Object.entries() - for of kv vs Object.entries() - forEach vs Object - for in

Created: 5 years ago by: Guest

Go to the latest result

Map - for of kv

Map - forEach

Object.entries() - for of kv

Object.entries() - forEach

Object - for in

Historical Performance Data aggregated from 128 community runs

Desktop Results:

Chrome 100 runs

Firefox 19 runs

Mobile Results:

Chrome 9 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `Map - for of kv vs Map - forEach vs Object.entries() - for of kv vs Object.entries() - forEach vs Object - for in`