Benchmark: For vs for of vs for in vs foreach vs map

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 of
for (var i of arr) { someFn(i); }
for in
for (var i in arr) { someFn(arr[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for
map
for of
for in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.106 Safari/537.36

Browser/OS: Chrome 91 on Windows 7

View result in a separate tab

Test name	Executions per second
foreach	5210.3 Ops/sec
for	2898.9 Ops/sec
map	4958.1 Ops/sec
for of	5572.2 Ops/sec
for in	2445.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Overview**

The provided JSON represents a benchmark that tests different ways to iterate over an array in JavaScript. The benchmark consists of six test cases:

1. `foreach`
2. `for`
3. `map`
4. `for of`
5. `for in`

Each test case uses the same script preparation code, which creates an empty array `arr` and defines a function `someFn(i)` that performs some calculations on the input `i`. The benchmark then measures how many times each test case executes the `someFn(i)` function.

**Options Compared**

The options compared in this benchmark are:

* `foreach`: Iterates over the array using a traditional for loop with an index variable (`i`).
* `for`: Iterates over the array using a for loop with an index variable (`i`), but without a length variable.
* `map`: Uses the `map()` method to create a new array with transformed values.
* `for of`: Iterates over the array using a for...of loop, which is a newer syntax introduced in ECMAScript 2015.
* `for in`: Iterates over the array using a traditional for loop with an index variable (`i`) and accessing each element using its property name.

**Pros and Cons**

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

* `foreach`:
	+ Pros: Well-established, widely supported.
	+ Cons: Can be less efficient due to the overhead of the traditional for loop.
* `for`:
	+ Pros: Simple and fast.
	+ Cons: May require explicit management of array length, which can lead to errors if not handled correctly.
* `map`:
	+ Pros: Creates a new array with transformed values, eliminating the need for additional memory allocation.
	+ Cons: Can be slower than traditional loops due to the overhead of creating a new array and iterating over it.
* `for of`:
	+ Pros: Modern, efficient, and easy to read.
	+ Cons: Requires support for the newer for...of loop syntax in older browsers or environments.
* `for in`:
	+ Pros: Simple and fast.
	+ Cons: May access each element using its property name, which can lead to unexpected behavior if not handled correctly.

**Library Usage**

None of the test cases use any external libraries. The `map()` method is a built-in JavaScript function that creates a new array with transformed values.

**Special JS Feature or Syntax**

The benchmark uses the newer for...of loop syntax introduced in ECMAScript 2015 (`for (var i of arr)`). This syntax allows iterating over an array without the need for explicit indexing.

**Other Considerations**

This benchmark is designed to test the performance and efficiency of different iteration methods in JavaScript. It's essential to consider factors like:

* Array size: The benchmark measures performance for arrays of varying sizes, which can affect the results.
* Browser support: The benchmark uses modern browser versions, but it's essential to ensure compatibility with older browsers or environments.
* Platform: The benchmark runs on a Windows 7 platform, but performance may vary on other platforms.

**Alternatives**

Some alternative approaches that could be used in a similar benchmark include:

* Using `reduce()` method to iterate over the array.
* Implementing custom iteration logic using recursive functions or closures.
* Comparing the performance of different iterator libraries (e.g., `iterator` package).

However, the provided benchmark is a good starting point for measuring the performance of traditional iteration methods in JavaScript.

Related benchmarks:

For vs for of vs for in vs foreach vs map (version: 0)

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

Created: 3 years ago by: Registered User

Jump to the latest result

foreach

for

map

for of

for in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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