Benchmark: for vs foreach vs some vs for..of and reduce

Script Preparation code:

var array = new Array(1000).map( () => 1);

Tests:

for
for (var i = 0; i < array.length; i++) { array[i]; }
foreach
array.forEach(function(i) { array[i]; });
some
array.some(function(i) { array[i]; });
for..of
for (var i of array) { array[i]; }
reduce
array.reduce( function(a, b ) { a+b; }, 1 )

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
foreach
some
for..of
reduce

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

The provided JSON represents a benchmark test that compares the performance of different loop constructs: `for`, `foreach`, `some`, and `for..of` with the additional `reduce` method. We'll break down each option, their pros and cons, and other considerations.

**Loop Constructs**

1. **For Loop (`for (var i = 0; i < array.length; i++) { ... }`)**:
	* Pros: Simple, efficient, and widely supported.
	* Cons: Can lead to off-by-one errors if not used carefully. It's a more manual approach, requiring the programmer to manage the loop variable.
2. **Foreach Loop (`array.forEach(function(i) { array[i]; });`)**:
	* Pros: Easy to read and write, as it doesn't require explicit indexing. The callback function is executed for each element in the array.
	* Cons: Can be slower than a `for` loop due to the overhead of the callback function invocation.
3. **Some Loop (`array.some(function(i) { array[i]; });`)**:
	* Pros: Similar to `foreach`, but returns a boolean indicating whether at least one element matches the condition.
	* Cons: Not as intuitive as `foreach` or `for`, as it implies a "some" success criterion. It can also lead to slower performance due to the callback function invocation.
4. **For..of Loop (`for (var i of array) { array[i]; }`)**:
	* Pros: Introduced in ECMAScript 2015, this loop is designed for iterating over arrays and other iterable objects. It's concise and easy to read.
	* Cons: Not as widely supported as older loop constructs. The `i` variable is also immutable, which might be surprising for some developers.

**Reduce Method**

1. **Reduce Method (`array.reduce(function(a, b) { a+b; }, 1)`)**:
	* Pros: Efficiently reduces an array to a single value (e.g., sum or product). It's often used in conjunction with other loop constructs.
	* Cons: May not be as intuitive for simple iteration tasks. The callback function expects the accumulator (`a`) and current element (`b`).

Now, let's consider special JavaScript features:

* **Arrow functions**: Used in `foreach`, `some`, and `reduce` to define small, anonymous functions. They're concise but can lead to issues if not used carefully (e.g., capturing outer scope variables).
* **Immutable variable declarations**: Used in the `for..of` loop to declare a new variable (`i`) that's reassigned on each iteration. This is a deliberate design choice to avoid mutable state.

Other alternatives for loop constructs:

* **Array.prototype.map()`: Not tested here, but it can be used to create a new array with transformed elements.
* **Array.prototype.filter()**: Also not tested here, as its primary purpose is data filtering rather than iteration.
* **Set or Map data structures**: Could potentially replace arrays in certain scenarios, especially for fast membership testing or key-value pairs. However, they're more complex and less intuitive for simple iteration tasks.

In summary, the benchmark test provides a fair comparison of different loop constructs and the `reduce` method, highlighting their strengths and weaknesses.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Browser/OS: Chrome 126 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for	15346.1 Ops/sec
foreach	479112.1 Ops/sec
some	467731.6 Ops/sec
for..of	25947.0 Ops/sec
reduce	469357.4 Ops/sec

Related benchmarks:

for vs foreach vs some vs for..of and reduce (version: 0)

Compare loop performance

Comparing performance of: for vs foreach vs some vs for..of vs reduce

Created: 2 years ago by: Guest

Jump to the latest result

for

foreach

some

for..of

reduce

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):