Benchmark: for vs for...in vs forEach

Script Preparation code:

arr = [];
arr.length = 800000;
arr.fill(0)

Tests:

for
let sum = 0; for (let i = 0; i < arr.length; i++) { sum += arr[i]; }
forEach
let sum = 0; arr.forEach(value => sum += value);
for...in
let sum = 0; for (let i in arr) { sum += i; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
forEach
for...in

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases.

**Benchmark Definition**

The benchmark is designed to compare the performance of three different approaches for iterating over an array in JavaScript:

1. `for` loop
2. `forEach` method (which is a part of the Array prototype)
3. `for...in` loop

**Script Preparation Code**

The script preparation code initializes an empty array `arr` with a length of 800,000 and fills it with zeros.

**Html Preparation Code**

There is no HTML preparation code provided.

**Test Cases**

There are three test cases:

1. **"for"`**
	* Benchmark Definition: A simple `for` loop that iterates over the array `arr`, adding each element to a running sum.
2. **"forEach"`**
	* Benchmark Definition: The same as the "for" case, but using the `forEach` method to iterate over the array.
3. **"for...in"`**
	* Benchmark Definition: A `for...in` loop that iterates over the array's own enumerable properties (i.e., its elements), adding each property value to a running sum.

**Options Compared**

The benchmark compares the performance of these three approaches in terms of:

* Number of executions per second (ExecutionsPerSecond)

**Pros and Cons**

1. **`for` loop**: This is a simple, straightforward approach that can be easily understood by many developers. However, it may not be as efficient as other options since it uses a fixed index `i`.
2. **`forEach` method**: This is a part of the Array prototype, which makes it easy to use and understand for developers familiar with JavaScript arrays. It's also relatively efficient, as it avoids the need for manual indexing.
3. **`for...in` loop**: This approach can be confusing for some developers since it iterates over the array's own properties (not its elements). However, it may not be as efficient as `forEach`, as it can involve additional overhead due to property lookup.

**Library and Special JS Feature**

None of these test cases rely on any specific JavaScript library or special feature. They only use built-in JavaScript functionality.

**Other Alternatives**

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

* `reduce()` method
* Arrow functions (e.g., `(arr, sum) => sum += arr[i]`)
* Spread syntax (`for (...i of arr) {...}`)
* Other iteration methods (e.g., `while` loop)

Keep in mind that the choice of alternatives will depend on the specific goals and requirements of the benchmark.

**Device Platform**

The latest benchmark results indicate that Chrome 85 running on a Windows Desktop is used for these tests.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4158.1 Safari/537.36

Browser/OS: Chrome 85 on Windows

View result in a separate tab

Test name	Executions per second
for	3.2 Ops/sec
forEach	91.3 Ops/sec
for...in	4.7 Ops/sec

Related benchmarks:

for vs for...in vs forEach (version: 1)

Comparing performance of: for vs forEach vs for...in

Created: 5 years ago by: Registered User

Jump to the latest result

for

forEach

for...in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):