Benchmark: Array map vs forEach

Script Preparation code:

   var arr = [];
   for (var i = 0; i < 100000; i++) {
       arr[i] = i;
   }

   function someFn(i) {
       return i * 3 * 8;
   }

Tests:

[].map
arr.map(item => someFn(item))
forEach
arr.forEach(function (item){ someFn(item); })

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:

No previous run results

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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.

**Benchmark Overview**

The test is comparing two approaches to iterate over an array of numbers: `Array.prototype.map()` and `Array.prototype.forEach()`. The goal is to determine which method is faster.

**Options Compared**

Two options are compared:

1. **`Array.prototype.map()`**: This method creates a new array with the results of applying a provided function on every element in the calling array.
2. **`Array.prototype.forEach()`**: This method executes the provided function once for each element in the calling array, but unlike `map()`, it does not create a new array.

**Pros and Cons**

* **`Array.prototype.map()`**:
	+ Pros: It creates a new array with the results, which can be useful if you need to process the original data without modifying it.
	+ Cons: It has higher overhead due to memory allocation and creation of a new array. However, this overhead is usually negligible for small to medium-sized datasets.
* **`Array.prototype.forEach()`**:
	+ Pros: It does not create a new array, which can be beneficial if you need to modify the original data or work with large datasets.
	+ Cons: It only allows executing the provided function once per element, whereas `map()` can execute the function multiple times (once for each element).

**Other Considerations**

* In modern JavaScript engines, both methods are optimized to use the same underlying native code. The difference lies in how they interact with the ECMAScript specification.
* Some JavaScript engines, like V8 (used by Google Chrome), have optimized `map()` and `forEach()` implementations that can be highly parallelized, which may affect performance.

**Library Used**

In this benchmark, no libraries are explicitly mentioned as being used. However, it's worth noting that some libraries or frameworks might use alternative methods to iterate over arrays, such as using `reduce()` or other custom functions.

**Special JS Feature or Syntax**

There is no special JavaScript feature or syntax being used in this benchmark. The code is written in plain JavaScript and adheres to the ECMAScript specification.

**Alternative Approaches**

If you're looking for alternative ways to iterate over arrays, consider the following:

* **`Array.prototype.reduce()`**: This method reduces an array to a single value by applying a provided function on every element in the array.
* **Custom iteration using `for...of` or `while` loops**: You can use these loops to manually iterate over an array, which might be faster for very large datasets due to less overhead.

Overall, the choice between `Array.prototype.map()` and `Array.prototype.forEach()` depends on your specific requirements and performance needs. If you need to create a new array with transformed data or work with small to medium-sized datasets, `map()` might be a better choice. For larger datasets or when working with the original data, `forEach()` could be more efficient.

Related benchmarks:

Array map vs forEach (version: 0)

Comparing performance of: [].map vs forEach

Created: 2 years ago by: Guest

Jump to the latest result

[].map

forEach

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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