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

Script Preparation code:

function generateTestArray() {
	var result = [];

	for (let i = 0; i < 1000000; ++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]; });
every
array.every(function(i) { array[i]; });
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	5.5 Ops/sec
for (reverse with length)	10.9 Ops/sec
some	5.6 Ops/sec
every	3697492.8 Ops/sec
forEach	5.6 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

MeasureThat.net provides a JavaScript microbenchmarking platform where users can create and run benchmarks to compare the performance of different approaches in their code. The provided benchmark is designed to test the performance of four common iteration methods in JavaScript: `for`, `forEach`, `some`, and `every`. The benchmark creates a large array of 1,000,000 objects and then iterates over it using each of these methods.

**Benchmark Definition**

The benchmark definition represents the script that will be executed by MeasureThat.net. In this case, there are four separate definitions:

*   **`for`**: Iterates over the array using a traditional `for` loop.
*   **`for (reverse with length)`**: Iterates over the array in reverse order using a `for` loop and stores the length of the array in a variable.
*   **`every`**: Iterates over the array using the `every()` method, which returns `true` if all elements pass the test.
*   **`forEach`**: Iterates over the array using the `forEach()` method.

**Library Used: None**

This benchmark does not use any external libraries. The script is self-contained and only relies on built-in JavaScript features.

**Options Compared**

The four options are compared in terms of their performance:

*   **`for`**: Uses a traditional `for` loop, which can be slower due to the overhead of incrementing the loop counter.
*   **`forEach`**: Uses the `forEach()` method, which is designed for iterating over arrays and has optimized performance.
*   **`some`** and **`every`**: These methods are designed for testing a single element or all elements in an array. While they can be faster than traditional loops, their performance may vary depending on the specific use case.

**Pros and Cons of Each Approach**

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

*   **`for`**: Pros: Simple to implement, easy to understand. Cons: Can be slower due to loop overhead.
*   **`forEach`**: Pros: Optimized performance, designed for array iteration. Cons: May not be suitable for all use cases.
*   **`some`** and **`every`**: Pros: Designed for specific use cases, optimized performance. Cons: May have slower execution times than traditional loops due to method overhead.

**Special JS Features or Syntax**

There are no special JavaScript features or syntax used in this benchmark.

**Other Alternatives**

If you're looking for alternative approaches to iterate over an array, consider using:

*   **`for...in`**: Iterates over the properties of an object. While not suitable for arrays, it can be used with some creative workarounds.
*   **`map()`**, **`filter()`, and **`reduce()`**: These methods are designed for functional programming and can be useful for array iteration in certain situations.

**Conclusion**

The provided benchmark demonstrates the performance differences between four common iteration methods in JavaScript: `for`, `forEach`, `some`, and `every`. By understanding the pros and cons of each approach, developers can choose the most suitable method for their specific use case.

Related benchmarks:

for vs for (reverse with length) vs every vs forEach with big array (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):