Benchmark: Array loop vs foreach vs map (cached length)

Script Preparation code:

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

Tests:

foreach
arr.forEach((item) => { someFn(item); })
for
var length = arr.length for (var i = 0, len = length; i < len; i++) { someFn(arr[i]); }
map
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

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmark test case on MeasureThat.net, which compares the performance of three different approaches for iterating over an array: `forEach`, `for` loop with cached length, and `map`. The benchmark measures how many executions per second each approach can perform.

**Benchmark Definition**

The benchmark definition is not provided in JSON format. However, based on the "Script Preparation Code" section, we know that the script starts by initializing an empty array `arr` and then populating it with 1000 elements using a loop. The function `someFn(i)` is defined to take an integer `i` as input and returns the result of `i * 3 * 8`.

**Options Compared**

The benchmark compares three different approaches:

1. **`forEach`**: This approach uses the `forEach` method of arrays, which executes a provided callback function once for each element in the array.
2. **`for` loop with cached length**: This approach uses a traditional `for` loop to iterate over the elements of the array, but caches the length of the array to avoid recalculating it on each iteration.
3. **`map`**: This approach uses the `map` method of arrays, which executes a provided callback function for each element in the array and returns a new array with the results.

**Pros and Cons**

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

*   **`forEach`**:
    *   Pros: Simple to implement, easy to read, and maintain.
    *   Cons: May have slower performance due to the overhead of calling the callback function for each element.
*   **`for` loop with cached length**:
    *   Pros: Can be faster than `forEach` since it avoids the overhead of callback function calls. The cached length can also reduce the number of iterations.
    *   Cons: More complex to implement, especially when dealing with arrays of varying lengths.
*   **`map`**:
    *   Pros: Returns a new array with the results, which can be useful in some cases. Can be faster than `forEach` since it avoids creating multiple callback function calls for each element.
    *   Cons: Creates a new array, which can consume more memory, especially for large arrays.

**Library and Purpose**

In this benchmark, no libraries are explicitly mentioned. However, the use of JavaScript's built-in methods (`forEach`, `map`) implies that the benchmark is testing the performance of these native methods.

**Special JS Features or Syntax**

This benchmark does not explicitly test any special JavaScript features or syntax. It focuses on comparing three fundamental approaches to iterating over arrays using standard JavaScript.

**Other Alternatives**

If you're interested in exploring alternative approaches for iterating over arrays, consider:

*   **`reduce()`**: A method that applies a callback function to each element of an array and reduces the output to a single value.
*   **`every()`** and `some()`: Methods that test whether all or some elements in an array satisfy a provided condition.
*   **Indexed loops**: Using traditional `for` loops with index variables can also provide better performance for certain use cases.

Keep in mind that the choice of iteration approach depends on your specific requirements, such as memory usage, performance, and code readability.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.60 Safari/537.36

Browser/OS: Chrome 100 on Windows

View result in a separate tab

Test name	Executions per second
foreach	14380.1 Ops/sec
for	7711.9 Ops/sec
map	14525.2 Ops/sec

Related benchmarks:

Array loop vs foreach vs map (cached length) (version: 0)

Comparing performance of: foreach vs for vs map

Created: 2 years ago by: Guest

Jump to the latest result

foreach

for

map

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):