Benchmark: Array concat() vs spread concat

Script Preparation code:

var arr1 = ['a', 'b'];
var arr2 = ['c', 'd'];

Tests:

Array.concat()
arr1.concat(arr2);
Spread concat
[...arr1, ...arr2]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.concat()
Spread concat

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/96.0.4664.110 Safari/537.36

Browser/OS: Chrome 96 on Windows

View result in a separate tab

Test name	Executions per second
Array.concat()	2872663.2 Ops/sec
Spread concat	2232480.8 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 benchmark and its options.

**Benchmark Definition json:**

The provided JSON defines a JavaScript microbenchmark with two test cases:

* `Array.concat()`: This test case measures the performance of the built-in `concat()` method for arrays in JavaScript.
* `Spread concat`: This test case measures the performance of the spread operator (`...`) when used to concatenate arrays.

**Options being compared:**

The two options being compared are:

1. **Built-in `concat()` method**: The traditional way to concatenate arrays in JavaScript.
2. **Spread operator (`...`)**: A newer feature introduced in ECMAScript 2015 (ES6) that allows for more concise and expressive array concatenation.

**Pros and Cons of each approach:**

* **Built-in `concat()` method**:
	+ Pros:
		- Widely supported and well-established.
		- Simple to use and understand.
	+ Cons:
		- Can be less efficient than the spread operator, especially for large arrays.
		- May involve more overhead due to string concatenation under the hood.
* **Spread operator (`...`)**:
	+ Pros:
		- More concise and expressive.
		- Can be faster and more efficient for large arrays.
	+ Cons:
		- Less widely supported in older browsers or environments (although most modern browsers support ES6+ features).
		- May require additional syntax knowledge.

**Library usage:**

There is no library used in this benchmark. The tests only involve built-in JavaScript functions and operators.

**Special JS feature or syntax:**

The spread operator (`...`) is a special syntax introduced in ECMAScript 2015 (ES6). It allows for more concise array concatenation, making it a more modern and expressive way to combine arrays.

**Other alternatives:**

For large-scale array concatenations, other approaches may be considered:

* **Using `Array.prototype.reduce()`**: Instead of using the spread operator or `concat()`, you can use `reduce()` to concatenate arrays. This approach requires creating a callback function, but can be more efficient for very large datasets.
* **Using `Array.prototype.push()`**: You can push elements from one array into another using `push()`. However, this method may not be as readable or concise as the spread operator or `concat()`.

Keep in mind that these alternatives may have different performance characteristics and use cases compared to the built-in methods and spread operator.

Related benchmarks:

Array concat() vs spread concat (version: 0)

Comparing performance of: Array.concat() vs Spread concat

Created: 3 years ago by: Guest

Jump to the latest result

Array.concat()

Spread 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):