Benchmark: forEach mutate object vs map spread copy v2

Tests:

map
const objects = [ { a: 'XzWtv', b: 'sFqrG', c: 'qCbnP' }, { a: 'yjkAu', b: 'vMhlE', c: 'xPqro' }, { a: 'wNztX', b: 'gDypR', c: 'iHklL' }, { a: 'mQjvs', b: 'dKzpt', c: 'aVbcO' }, { a: 'bUefZ', b: 'cRiyG', c: 'uTqxs' } ] objects.map(el => ({...el, d: Math.random()}))
forEach
const objects = [ { a: 'XzWtv', b: 'sFqrG', c: 'qCbnP' }, { a: 'yjkAu', b: 'vMhlE', c: 'xPqro' }, { a: 'wNztX', b: 'gDypR', c: 'iHklL' }, { a: 'mQjvs', b: 'dKzpt', c: 'aVbcO' }, { a: 'bUefZ', b: 'cRiyG', c: 'uTqxs' } ] objects.forEach(el => {el.d = Math.random()})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
map
forEach

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36

Browser/OS: Chrome 137 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
map	17035556.0 Ops/sec
forEach	22954522.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested.

**Benchmark Definition**

The website MeasureThat.net allows users to create custom JavaScript benchmarks. In this case, we have a single benchmark definition that compares two approaches:

1. Using `forEach` to mutate an object
2. Using `map` with spread syntax to create a new object

**Options Being Compared**

Two options are being compared in this benchmark:

### 1. `forEach`

This approach uses the `forEach` method to iterate over an array of objects, modifying each object in place by adding a new property (`d`) with a random value.

```javascript
objects.forEach(el => {el.d = Math.random()})
```

**Pros and Cons**

* Pros:
	+ Simple and straightforward implementation
	+ No need to create a new object or manipulate the original array
* Cons:
	+ May incur performance overhead due to iteration over the entire array

### 2. `map` with Spread Syntax

This approach uses the `map` method to create a new array of objects, where each object is a copy of the original object with an additional property (`d`) added using the spread syntax (`{...el, d: Math.random()}`).

```javascript
objects.map(el => ({...el, d: Math.random()}))
```

**Pros and Cons**

* Pros:
	+ More efficient than `forEach`, as it avoids iteration over the entire array
	+ Creates a new object without modifying the original array
* Cons:
	+ May incur overhead due to creating a new array

**Library and Special JS Features**

In this benchmark, there is no explicit library being used. However, the use of spread syntax (`{...el, d: Math.random()}`) demonstrates modern JavaScript's feature-rich syntax.

**Device and Browser Information**

The latest benchmark results show that Chrome 126 on a Windows desktop produces higher execution counts for both `forEach` and `map` approaches compared to the previous version. This suggests that the performance differences between these two approaches may be platform-dependent or dependent on specific browser optimizations.

**Alternative Approaches**

Other alternatives for achieving similar results could include:

* Using `reduce` instead of `forEach`
* Utilizing array methods like `filter`, `slice`, or `concat`
* Employing more advanced techniques, such as using a custom iterator or using WebAssembly (if applicable)

These alternative approaches would likely have different performance characteristics and may not be suitable for all use cases.

Related benchmarks:

forEach mutate object vs map spread copy v2 (version: 0)

add field into object with forEach vs spread fields into new object with new field in array of objects

Comparing performance of: map vs forEach

Created: one year ago by: Guest

Jump to the latest result

map

forEach

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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