Benchmark: concat vs spread three arrays

Script Preparation code:

var a = [1, 2, 3, 4, 5];
var b = [6, 7, 8, 9, 10, 11];
var c= [12, 13, 14, 15, 16];

Tests:

concat
var res = [].concat(a, b, c);
spread
var res = [...a, ...b, ...c];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
concat
spread

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser/OS: Chrome 123 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
concat	5467685.5 Ops/sec
spread	7476074.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested, compared, and discussed in this JavaScript microbenchmark.

**What is being tested?**

The benchmark compares two approaches to concatenate three arrays: using the `concat()` method versus the spread operator (`...`).

**Options compared:**

1. **Concatenation using `concat()`**: This method creates a new array by concatenating the input arrays.
2. **Spread operator (`...`)**: This syntax allows you to "spread" the elements of an iterable (like an array) into another iterable.

**Pros and Cons:**

* **Concatenation using `concat()`:**
	+ Pros:
		- Widespread support in older browsers (pre-ES6).
		- Easy to read and understand.
	+ Cons:
		- Creates a new array, which can lead to performance issues for large datasets.
		- Can be slower compared to the spread operator.
* **Spread operator (`...`):**
	+ Pros:
		- More concise and expressive than `concat()`.
		- Creates a shallow copy of the original arrays, preserving references.
	+ Cons:
		- Requires support for ES6 syntax (introduced in Chrome 57, Firefox 48, etc.).
		- Can be slower due to the creation of a new array object.

**Library and its purpose:**

There is no explicit library used in this benchmark. The spread operator is a built-in JavaScript feature introduced in ECMAScript 2015 (ES6).

**Special JS feature or syntax:**

The benchmark uses the spread operator (`...`), which was introduced in ES6. This allows for more concise and expressive array concatenation.

**Other considerations:**

* Performance: The benchmark measures the execution speed of both approaches, likely to determine which one is faster.
* Memory usage: Creating a new array using `concat()` may lead to higher memory usage compared to the spread operator, which creates a shallow copy of the original arrays.

**Alternative approaches:**

1. **Array.prototype.push()**: This method modifies the original array in-place, eliminating the need for a new array or spreading elements.
2. **Array.prototype.splice()**: This method also modifies the original array in-place and can be used to concatenate arrays.
3. **Array.prototype.slice() + Array.prototype.concat()**: Another approach is to use `slice()` to create a shallow copy of the original array and then concatenate it using `concat()`.

However, these alternatives are not explicitly tested or compared in this benchmark, focusing instead on the spread operator versus `concat()`.

Related benchmarks:

concat vs spread three arrays (version: 0)

Compare the spread operator with the concat() method

Comparing performance of: concat vs spread

Created: 2 years ago by: Guest

Jump to the latest result

concat

spread

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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