Benchmark: Concat many arrays

Script Preparation code:

const getRandomNumber = (max = 1, min = 0) =>
  Math.round(Math.random() * (max - min) + min);

window.arrays = new Array(100).fill().map(() => {
    const l = getRandomNumber(20, 10);
    const val = getRandomNumber(100);
    return new Array(l).fill(val);
  });

Tests:

Chained concat
let result = []; arrays.forEach(a => result = result.concat(a));
Single concat
const result = [].concat.apply([], arrays);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Chained concat
Single concat

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Safari/605.1.15

Browser/OS: Safari 13 on Mac OS X 10.15.3

View result in a separate tab

Test name	Executions per second
Chained concat	10275.7 Ops/sec
Single concat	111150.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what's being tested.

**Benchmark Definition**

The benchmark is designed to compare two approaches for concatenating arrays in JavaScript:

1. **Chained Concat**: This approach uses the `concat()` method in a chained manner, where the result of each concatenation operation is assigned back to the `result` variable.
2. **Single Concat**: This approach uses the `concat()` method with the `apply()` method to concatenate all arrays at once.

**Options Compared**

The two options are being compared in terms of their performance impact on the browser's JavaScript engine. The goal is to determine which approach is faster and more efficient.

**Pros and Cons**

Here are some pros and cons for each approach:

* **Chained Concat**:
	+ Pros: Easy to understand and implement, as it mimics how people typically concatenate arrays.
	+ Cons: Can lead to unnecessary assignments and reassignments of the `result` variable, which can slow down the execution.
* **Single Concat**:
	+ Pros: Reduces the number of assignments and reassignments, potentially leading to better performance.
	+ Cons: May be less intuitive for developers who are not familiar with the `apply()` method.

**Library Used**

In this benchmark, there is no explicit library being used. The JavaScript engine's built-in `Array.prototype.concat()` method is being tested.

**Special JS Feature/Syntax**

There is a special syntax used in this benchmark: `fill()`. This method creates a new array filled with a specified value. It's not explicitly mentioned in the documentation, but it's an important feature of modern JavaScript arrays.

**Other Considerations**

When running benchmarks like this one, it's essential to consider factors such as:

* Browser version and engine
* Device platform and operating system
* Execution environment (e.g., Node.js, WebKit)
* Number of test runs and sample size

These factors can affect the results and provide a more accurate representation of performance in real-world scenarios.

**Alternatives**

Other approaches for concatenating arrays in JavaScript include:

1. Using `Array.prototype.reduce()` or `Array.prototype.forEach()`
2. Utilizing native WebAssembly (WASM) APIs
3. Employing optimized array concatenation libraries

However, these alternatives are not being tested in this specific benchmark.

In summary, the benchmark is designed to compare two approaches for concatenating arrays: chained concat and single concat. The test aims to determine which approach provides better performance on modern JavaScript engines.

Related benchmarks:

Concat many arrays (version: 0)

Concat chain VS single concat

Comparing performance of: Chained concat vs Single concat

Created: 4 years ago by: Guest

Jump to the latest result

Chained concat

Single concat

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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