Benchmark: for vs forEach vs for in vs for of (2)

Script Preparation code:

var arr = [];

function doMath(a) {
  return Math.log(a);
}

for(i=0; i<10000; i++){
  arr[i] = i + 1;
}

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
for in
for
for of

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

I'll provide an in-depth explanation of the benchmark, its test cases, and options being compared.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark named "for vs forEach vs for in vs for of (2)". The purpose of this benchmark is to compare the performance of four different iteration mechanisms: `for`, `forEach`, `for...in`, and `for...of`. These iteration mechanisms are commonly used in JavaScript to iterate over arrays or other iterable objects.

**Options Being Compared**

The options being compared are:

1. **`for` loop**: This is a traditional loop that uses an index variable (`i`) to access elements of the array.
2. **`forEach` method**: This is a built-in method that iterates over an array using a callback function.
3. **`for...in` loop**: This is a loop that iterates over the properties (including indices) of an object, including arrays.
4. **`for...of` loop**: This is a loop that iterates over the values of an iterable object, such as an array.

**Pros and Cons**

Each iteration mechanism has its pros and cons:

1. **`for` loop**:
	* Pros: More control over indexing and looping behavior.
	* Cons: Can be slower due to overhead of manual indexing and looping logic.
2. **`forEach` method**:
	* Pros: Concise and readable code, no need to worry about indexing.
	* Cons: May incur additional overhead due to function invocation.
3. **`for...in` loop**:
	* Pros: Allows iteration over object properties, including indices.
	* Cons: Can be slower due to unnecessary iterations over undefined properties.
4. **`for...of` loop**:
	* Pros: Concise and readable code, no need to worry about indexing.
	* Cons: May not work as expected for arrays with non-numeric indices.

**Library Usage**

None of the test cases explicitly uses a library, but `forEach` method relies on the built-in `Array.prototype.forEach` function. However, since this is a microbenchmark, the focus is on the iteration mechanisms rather than external libraries.

**Special JavaScript Features or Syntax**

No special JavaScript features or syntax are used in these benchmark test cases. The examples are straightforward and do not include any advanced topics like async/await, closures, or modern ES6+ features.

**Other Alternatives**

In addition to the four options being compared, other iteration mechanisms exist in JavaScript, such as:

1. **`map` method**: This creates a new array with the results of applying a provided function to each element.
2. **`reduce` method**: This applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.

These alternatives are not included in the benchmark, as they focus specifically on loop-based iteration mechanisms.

I hope this explanation helps you understand the JavaScript microbenchmark!

Latest run results:

Run details: (Test run date: 7 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36

Browser/OS: Chrome 125 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
forEach	484.2 Ops/sec
for in	382.0 Ops/sec
for	339.1 Ops/sec
for of	535.7 Ops/sec

Related benchmarks:

for vs forEach vs for in vs for of (2) (version: 0)

for vs forEach vs for in vs for of

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

Created: 4 years ago by: Guest

Jump to the latest result

forEach

for in

for

for of

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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