Benchmark: Array loop vs foreach vs map into array 2

Script Preparation code:

var arr = [];

for (let i = 0; i < 1000; i++) {
  arr[i] = i;
}
  
function someFn(i) {
  return i * 3 * 8;
}

Tests:

foreach
let newArray = [] arr.forEach(function (item){ newArray.push(someFn(item)); })
for
let newArray = [] for (let i = 0; i < arr.length; i++) { newArray.push(someFn(arr[i])); }
map
let newArray = arr.map(item => someFn(item))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for
map

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the provided benchmark and its various aspects.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark, specifically designed to compare the performance of three different approaches: Array loops with `for` loops, `forEach` loops, and `map` function.

**Benchmark Definition**

The benchmark definition provides two types of code:

1. **Script Preparation Code**: This is the initial script that creates an array `arr` with 1000 elements and defines a function `someFn` that takes an integer `i` as input and returns the result of `i * 3 * 8`.
2. **Html Preparation Code** (not used in this benchmark): This section would typically contain HTML code to set up the environment for running the benchmarks.

**Individual Test Cases**

The benchmark consists of three test cases, each comparing a different approach:

1. **`foreach` Loop**: The code uses `arr.forEach()` to iterate over the array and push the result of `someFn(item)` into a new array.
2. **`for` Loop**: The code uses a traditional `for` loop to iterate over the array and push the result of `someFn(arr[i])` into a new array.
3. **`map` Function**: The code uses the `map()` function to create a new array with the results of applying `someFn(item)` to each element in the original array.

**Library Usage**

None of the provided test cases use any external libraries.

**Special JavaScript Features/Syntax**

The benchmark uses the following special JavaScript features/syntax:

* The `forEach` loop and `map` function are part of the ECMAScript standard, but their implementation may vary across browsers.
* The `for...of` loop is not used in this benchmark, as it is not supported by older browsers.

**Performance Considerations**

The performance differences between these approaches can be significant due to the following factors:

* **Cache locality**: In the `for` loop and `map` function, elements are accessed sequentially, which may improve cache locality. In contrast, the `forEach` loop iterates over the array, which may lead to more cache misses.
* **Iteration overhead**: The `forEach` loop has an iteration overhead due to the callback function being called for each element, while the `for` loop and `map` function do not have this overhead.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

1. **`foreach` Loop**:
	* Pros: Easy to read and write, flexible.
	* Cons: May have higher iteration overhead due to callback functions.
2. **`for` Loop**:
	* Pros: Good cache locality, lower iteration overhead.
	* Cons: Less readable and more verbose than `forEach`.
3. **`map` Function**:
	* Pros: More concise and readable, good cache locality.
	* Cons: May have limited control over iteration order.

**Alternatives**

Other alternatives to consider when working with arrays in JavaScript include:

* Using `Array.prototype.reduce()` for aggregation tasks
* Utilizing `Set` or `Map` data structures for faster lookups and insertions
* Leveraging `slice()` or `subarray()` methods for array slicing

Keep in mind that the choice of approach depends on the specific requirements and constraints of your project.

Related benchmarks:

Array loop vs foreach vs map into array 2 (version: 0)

Comparing performance of: foreach vs for vs map

Created: 3 years ago by: Guest

Jump to the latest result

foreach

for

map

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):