Benchmark: Concat vs foreach vs for

Tests:

Concat
const items = Array.from(Array(40000).keys()); const items2 = Array.from(Array(40000).keys()); const items3 = items.concat(items2);
for i
const p1 = Array.from(Array(40000).keys()); const p2 = Array.from(Array(40000).keys()); const p2Length = p2.length; const p1Length = p1.length; p1.length = p1Length + p2Length; for (let i = 0; i < p2Length; i++) { p1[p1Length + i] = p2[i]; }
for of
const items = Array.from(Array(40000).keys()); const items2 = Array.from(Array(40000).keys()); for (const element of items) { items2.push(element); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Concat
for i
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.

Let's break down the benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark is comparing three different approaches to concatenate arrays in JavaScript:

1. `concat()`
2. `for...of` loop
3. `for...i` loop

**What are we testing?**

We're testing which approach is faster, with the goal of understanding how JavaScript engines optimize array concatenation.

**Options Compared**

The three options being compared are:

* `concat()`: A built-in method that concatenates two or more arrays.
* `for...of` loop: A loop construct that iterates over an iterable object (in this case, an array).
* `for...i` loop: A traditional loop construct that uses a counter variable to iterate.

**Pros and Cons of Each Approach**

1. **concat()**:
	* Pros: Simple and straightforward.
	* Cons: Creates a new array with the concatenated elements, which can be memory-intensive for large arrays.
2. **for...of** loop:
	* Pros: Efficient use of memory, as it only iterates over one array at a time.
	* Cons: Can be slower due to the loop overhead and potential caching issues.
3. **for...i** loop:
	* Pros: Fastest execution, as it uses a traditional loop construct that's optimized by most JavaScript engines.
	* Cons: Uses more memory than `concat()`, as each iteration creates a new element in the array.

**Library Used**

There is no explicit library used in this benchmark. The only library being utilized is the built-in `Array.from()` function, which returns an array from an iterable object (in this case, an array of indices).

**Special JS Features/Syntax**

The benchmark uses a special JavaScript feature: the `for...of` loop, which was introduced in ECMAScript 2015 (ES6). This loop construct allows you to iterate over arrays and other iterable objects without using an index variable.

**Other Alternatives**

Some alternative approaches that could be tested in this benchmark include:

* Using `Array.prototype.push()` instead of concatenating arrays.
* Using a third-party library like Lodash's `concatArrays` function.
* Using native WebAssembly support for array operations (if available).

However, these alternatives might not be directly comparable to the three options being tested here, as they may have different performance characteristics or use additional resources.

In conclusion, this benchmark helps us understand how JavaScript engines optimize array concatenation and which approach is fastest. The results can provide valuable insights for developers who need to perform array concatenations in their code.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36

Browser/OS: Chrome 118 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Concat	788.2 Ops/sec
for i	803.4 Ops/sec
for of	820.7 Ops/sec

Related benchmarks:

Concat vs foreach vs for (version: 0)

Comparing performance of: Concat vs for i vs for of

Created: one year ago by: Guest

Jump to the latest result

Concat

for i

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):