Benchmark: for vs for (reverse with length) vs every vs forEach with small array 2

Script Preparation code:

function generateTestArray() {
	var result = [];

	for (let i = 0; i < 100; ++i) {
		result.push({
			a: i,
			b: i / 2,
			r: 0,
		});
	}

	return result;
}

var array = generateTestArray();

Tests:

for
for (var i = 0; i < array.length; i++) { array[i]; }
for (reverse with length)
var length = array.length; for (var i = length; --i >= 0;) { array[i]; }
some
array.some(function(i) { array[i]; return false; });
every
array.every(function(i) { array[i]; return true; });
forEach
array.forEach(function(i) { array[i]; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
for (reverse with length)
some
every
forEach

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36

Browser/OS: Chrome 97 on Windows

View result in a separate tab

Test name	Executions per second
for	64476.5 Ops/sec
for (reverse with length)	122596.5 Ops/sec
some	69515.5 Ops/sec
every	71307.5 Ops/sec
forEach	71266.6 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 5 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks and explore what's being tested on MeasureThat.net.

**Benchmark Overview**

The benchmark is comparing four different approaches to iterate over an array:

1. `for` loop
2. `for (reverse with length)` loop, which reverses the iteration order and uses the length property to access elements
3. `every` method, which returns `true` if all elements pass a test
4. `forEach` method, which executes a callback function for each element

**Options Compared**

The benchmark is comparing two options:

* **`for` loop**: A traditional, iterative approach that uses a counter variable to access each element in the array.
* **`for (reverse with length)` loop**: An optimized version of the `for` loop that reverses the iteration order and uses the length property to access elements. This approach can be faster because it reduces the number of array accesses.

**Pros and Cons**

Here's a brief summary of each approach:

* **`for` loop**:
	+ Pros: Simple, easy to understand, and works well for most use cases.
	+ Cons: Can be slower due to unnecessary array accesses.
* **`for (reverse with length)` loop**:
	+ Pros: Optimized for arrays, reduces number of array accesses, and can be faster.
	+ Cons: May be less intuitive for developers who are not familiar with this approach.

**Library Usage**

In the benchmark code, the `some`, `every`, and `forEach` methods are used, which are part of the JavaScript API. These methods are:

* **`some()`**: Returns `true` if at least one element passes a test.
* **`every()`**: Returns `true` if all elements pass a test.
* **`forEach()`**: Executes a callback function for each element in an array.

These methods are useful when working with arrays, but they may be slower than manual loops due to the overhead of function calls and object lookups.

**Special JS Features**

None of the benchmark code uses any special JavaScript features, such as `let` or `const`, arrow functions, or modern syntax like async/await.

**Alternatives**

If you're interested in optimizing array iteration, here are some alternatives:

* **Manual loops**: You can use a simple `for` loop to iterate over an array. This approach is often faster because it avoids the overhead of function calls and object lookups.
* **Array methods with callbacks**: Instead of using `some`, `every`, or `forEach`, you can use manual loops and callbacks to achieve similar results.
* **Native array methods with optimizations**: Some browsers have optimized native array methods, such as `forEach` and `map`, which can be faster than their JavaScript counterparts.

Keep in mind that the best approach depends on your specific use case, performance requirements, and personal preference.

Related benchmarks:

for vs for (reverse with length) vs every vs forEach with small array 2 (version: 0)

Comparing performance of: for vs for (reverse with length) vs some vs every vs forEach

Created: 3 years ago by: Guest

Jump to the latest result

for

for (reverse with length)

some

every

forEach

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 5 months ago):