Benchmark: Hungry js map vs forEach

Script Preparation code:

// Create sample data
var array = [];
array.forEach( i => array.push(i) );

var manipulateFn = num => {
	return num * 2 * 3;
}

Tests:

map
var newArray = array.map( i => manipulateFn(i));
forEach
array.forEach( i => { manipulateFn(i); });

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: 2 months ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 26_3_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/145.0.7632.108 Mobile/15E148 Safari/604.1

Browser/OS: Chrome Mobile iOS 145 on iOS 26.3.0

View result in a separate tab

Test name	Executions per second
map	59229580.0 Ops/sec
forEach	497333984.0 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's being tested, compared, and considered.

**Benchmark Overview**

The test compares the performance of two approaches to manipulate an array: `forEach` and `map`. The sample data is created using the preparation code, which initializes an empty array `array` and populates it with numbers using a closure function `manipulateFn`.

**Options Compared**

The benchmark tests the following options:

1. **`forEach`**: Iterates over each element in the array, applying the `manipulateFn` to each one.
2. **`map`**: Creates a new array by transforming each element in the original array using the `manipulateFn`.

**Pros and Cons**

* **`forEach`**:
	+ Pros: Easy to understand, straightforward approach. It's often used for iteration when you don't need to collect the results.
	+ Cons: Can be slower than `map` because it iterates over the array multiple times (once per element), which can lead to unnecessary computations and memory allocations.
* **`map`**:
	+ Pros: More concise, efficient way to transform an array. It returns a new array with the results, making it easier to work with.
	+ Cons: Can be less intuitive for beginners, as it changes the original array.

**Library and Special JavaScript Features**

There are no specific libraries used in this benchmark. However, some special JavaScript features are employed:

* **Closure**: The `manipulateFn` is defined inside another function (the preparation code), which creates a closure. This allows the `manipulateFn` to access the outer scope's variables.
* **Template Literals** (`\r\n\t`): Used in the benchmark's preparation code for formatting.

**Other Considerations**

The benchmark doesn't account for factors like:

* Array size and its impact on performance
* Browser-specific optimizations or quirks
* The specific use case of manipulating arrays (e.g., if you need to keep track of original indices)

**Alternatives**

Some alternative approaches to manipulating arrays include:

* Using a `for` loop: `for (var i = 0; i < array.length; i++) { manipulateFn(array[i]); }`
* Using `reduce()`: `array.reduce((acc, curr) => acc + manipulateFn(curr), 0)`
* Using `every()` and `some()`: These methods can be useful for iterating over arrays, but they're not as straightforward to use as `forEach` or `map`.

Keep in mind that the performance difference between these approaches may vary depending on the specific scenario and implementation details.

Related benchmarks:

Hungry js map vs forEach (version: 0)

Comparing performance of: map vs forEach

Created: 7 years 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):