Benchmark: Array loop vs foreach vs map vs for --

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(function (item){ someFn(item); })
for
for (var i = 0, len = arr.length; i < len; i++) { someFn(arr[i]); }
map
arr.map(item => someFn(item))
for --
for (var len = arr.length - 1; len >= 0; len--) { someFn(arr[len]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for
map
for --

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

I'll explain the benchmark and its options in detail.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark that compares the performance of four different approaches to iterate over an array: `forEach`, `for` loop, `map`, and a variation of the `for` loop (`for --`). The benchmark is designed to measure the execution time of each approach on a specific test case.

**Script Preparation Code**

The script preparation code creates an empty array `arr` with 1000 elements, initializes it with values from 0 to 999 using a `for` loop, and defines a function `someFn(i)` that takes an integer `i` as input and returns the result of multiplying `i` by 3 and 8.

**Benchmark Definitions**

The benchmark consists of four individual test cases:

1. **forEach**: Iterates over the array using the `forEach` method, applying the `someFn` function to each element.
2. **for**: Iterates over the array using a traditional `for` loop, applying the `someFn` function to each element.
3. **map**: Uses the `map` method to create a new array with the results of applying the `someFn` function to each element in the original array.
4. **for --**: Iterates over the array using a traditional `for` loop, but starts from the last index and decrements it until it reaches 0.

**Comparison**

The benchmark compares the performance of these four approaches by measuring the execution time for each test case. The results are reported as the number of executions per second (ExecutionsPerSecond) for each browser and device platform combination.

**Options Comparison**

Here's a comparison of the options:

* **forEach**: This approach uses the built-in `forEach` method, which is designed to iterate over arrays in a concise way. However, it may incur additional overhead due to the creation of an internal iterator object.
* **for**: This approach uses a traditional `for` loop, which can be slower than other approaches but provides more control and flexibility. The loop variable `i` must be explicitly incremented or decremented.
* **map**: This approach uses the `map` method, which creates a new array with transformed elements. While it's often used for mapping functions, it may incur additional overhead due to the creation of a new array.
* **for --**: This variation of the traditional `for` loop starts from the last index and decrements it until reaching 0. It provides more control over the iteration order but can be slower than other approaches.

**Pros and Cons**

Here are some pros and cons for each approach:

* **forEach**: Pros: concise, readable, and maintainable; Cons: may incur additional overhead due to internal iterator object.
* **for**: Pros: provides more control and flexibility; Cons: can be slower and less readable than other approaches.
* **map**: Pros: creates a new array with transformed elements; Cons: may incur additional overhead due to the creation of a new array.
* **for --**: Pros: provides more control over iteration order; Cons: can be slower and less readable than other approaches.

**Library Usage**

The benchmark uses the `forEach` method, which is a built-in JavaScript library. The `map` method also relies on the internal iterator object, but its purpose is primarily to create new arrays with transformed elements.

**Special JS Feature or Syntax**

There's no special JavaScript feature or syntax mentioned in the provided code snippet.

**Alternatives**

If you want to explore alternative approaches for iterating over arrays, consider:

* Using `reduce()` method instead of `forEach` or traditional loops.
* Utilizing array methods like `filter()`, `sort()`, or `slice()` depending on your use case.
* Leveraging libraries like Lodash or Ramda for more functional programming styles.
* Implementing custom iteration logic using techniques like iterator protocols or WebAssembly.

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

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.75 Safari/537.36

Browser/OS: Chrome 68 on Mac OS X 10.13.5

View result in a separate tab

Test name	Executions per second
foreach	15395.1 Ops/sec
for	7819.6 Ops/sec
map	14371.4 Ops/sec
for --	7746.0 Ops/sec

Related benchmarks:

Array loop vs foreach vs map vs for -- (version: 2)

Comparing performance of: foreach vs for vs map vs for --

Created: 6 years ago by: Registered User

Jump to the latest result

foreach

for

map

for --

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):