Benchmark: for vs foreach vs some [with effects]

Script Preparation code:

var array = new Array(100);

Tests:

for..in
for (var i in array) { console.log(array[i]); }
foreach
array.forEach(function(item, index) { console.log(item); return item; });
some
const result = array.some(function(item, index) { console.log(item); return item === array[index]; }); console.log(result);
for
for (var i = 0; i < array.length; i++) { console.log(array[i]); }
for with predefined size
var size = array.length for (var i = 0; i < size; i++) { console.log(array[i]); }
while
while((a=array.pop()) !== undefined){ console.log(array); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for..in
foreach
some
for
for with predefined size
while

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmarking test, and its purpose is to compare the performance of different loop constructs in JavaScript.

Let's break down each option:

**1. for (var i in array)**: This loop iterates over the `array` object using the `for...in` loop construct. The pros of this approach are that it does not require an explicit index variable, and it can be used to iterate over objects with non-numeric keys.

Cons:
* Performance is generally slower compared to other options.
* It's not designed for iterating over arrays or objects with numeric indices.
* In modern JavaScript, `for...in` should be avoided due to potential issues with object property iteration.

**2. foreach**: This loop uses the `forEach` method, which is a part of the ECMAScript standard since ES6. The pros are that it's concise and readable, and it doesn't require an explicit index variable.
* Cons:
	+ Not all older JavaScript engines support `forEach`.
	+ May not be optimized for performance.

**3. some**: This loop uses the `some` method, which returns a boolean value indicating whether at least one element of the array meets the condition. The pros are that it's concise and can be used to iterate over arrays.
* Cons:
	+ Not designed for iterating over all elements in the array.
	+ May not be optimized for performance.

**4. for (var i = 0; i < array.length; i++)**: This loop uses a traditional `for` loop with an explicit index variable. The pros are that it's widely supported and can be optimized for performance.
* Cons:
	+ Requires an explicit index variable, which can lead to off-by-one errors.

**5. for (var i = 0; i < size; i++)**: This loop uses a traditional `for` loop with a predefined size variable. The pros are that it's widely supported and allows for caching the array length.
* Cons:
	+ Requires an explicit size variable, which can lead to off-by-one errors.

**6. while (condition) { ... }**: This loop uses a `while` loop with a conditional statement. The pros are that it's flexible and can be used in various scenarios.
* Cons:
	+ May not be optimized for performance compared to other options.

The test cases also include the following considerations:

*   The use of `array.pop()` in the "while" loop case is an interesting approach, as it leverages the array's internal buffer to iterate over the elements. This can provide a more efficient solution, especially when dealing with large arrays.
*   The "for..in" loop is intentionally slow due to its inherent nature and potential issues with object property iteration.

To get the most out of these benchmarking results, consider the following:

*   Compare the execution times for different loops on various platforms, including older engines that may not support newer methods like `forEach`.
*   Look for patterns in performance differences across different browsers or devices.
*   Consider the trade-offs between performance, readability, and conciseness when choosing a loop construct.

For developers looking to optimize their JavaScript code, understanding the pros and cons of these different approaches will help them make informed decisions about which loops to use in specific situations.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.6.1 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 15 on iOS 15.6.1

View result in a separate tab

Test name	Executions per second
for..in	4908057.0 Ops/sec
foreach	659214.1 Ops/sec
some	294716.0 Ops/sec
for	14827.1 Ops/sec
for with predefined size	13938.3 Ops/sec
while	4873671.0 Ops/sec

Related benchmarks:

for vs foreach vs some [with effects] (version: 0)

Compare loop performance

Comparing performance of: for..in vs foreach vs some vs for vs for with predefined size vs while

Created: 2 years ago by: Registered User

Jump to the latest result

for..in

foreach

some

for

for with predefined size

while

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):