Benchmark: Array.prototype.concat vs splice for joining two arrays test2

Script Preparation code:

var a = Array(50).map(i => Math.random());
var b = Array(50).map(i => Math.random());

Tests:

immutable with concat
var other = a.concat(b)
direct mutation with splice + spread
a.splice(0, a.length, ...b);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
immutable with concat
direct mutation with splice + spread

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark is comparing two approaches to join two arrays: using `Array.prototype.concat()` (immutable) and using `Array.prototype.splice()` with spreading the second array (`...b`) (direct mutation).

**What is being tested?**

In this benchmark, we're testing which approach is faster for joining two arrays. The test cases:

1. Create two random arrays of length 50 using the `map()` function.
2. In each test case, one of the following operations is performed:
	* Using `concat()`: The resulting array is assigned to a new variable (`var other = a.concat(b)`).
	* Using `splice()` with spreading: The second array is appended to the first array using `splice()`, and then the result is assigned to a new variable (`a.splice(0, a.length, ...b);`).

**Options Compared**

The benchmark is comparing two approaches:

1. **Immutable approach (concat())**: Creates a new array by concatenating the two input arrays.
2. **Direct mutation approach (splice() with spreading)**: Modifies the first array in-place by appending the second array.

**Pros and Cons of Each Approach**

**Immutable Approach (concat()):**

Pros:

* Safer, as it doesn't modify the original array.
* Easier to understand and maintain.

Cons:

* Creates a new array, which can lead to increased memory allocation and garbage collection.
* May be slower due to the overhead of creating a new array.

**Direct Mutation Approach (splice() with spreading):**

Pros:

* Faster, as it modifies the existing array without creating a new one.
* Can be more efficient in terms of memory usage.

Cons:

* Modifies the original array, which can lead to unexpected behavior if not handled carefully.
* More complex and harder to understand for some developers.

**Library Used (none)**

There are no external libraries used in this benchmark.

**Special JS Feature or Syntax**

None mentioned. The benchmark only uses standard JavaScript features and syntax.

**Alternative Approaches**

Other approaches that might be considered:

1. Using `Array.prototype.push()` instead of `concat()`: This would still create a new array, but with the advantage of not modifying the original array.
2. Using `Array.prototype.concat()` with an empty array as the initial value: This would avoid creating a new array altogether, but would require careful handling to avoid unexpected behavior.
3. Using a library like Lodash or Ramda for array manipulation: These libraries often provide optimized and efficient implementations of common array operations.

In summary, this benchmark is testing the performance difference between two approaches to join arrays in JavaScript: using `Array.prototype.concat()` (immutable) versus `Array.prototype.splice()` with spreading (direct mutation). The immutable approach creates a new array, while the direct mutation approach modifies the existing array. The choice of approach depends on the specific use case and trade-offs between safety, performance, and maintainability.

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36

Browser/OS: Chrome 100 on Linux

View result in a separate tab

Test name	Executions per second
immutable with concat	2910623.2 Ops/sec
direct mutation with splice + spread	2011289.6 Ops/sec

Related benchmarks:

Array.prototype.concat vs splice for joining two arrays test2 (version: 0)

Comparing performance of: immutable with concat vs direct mutation with splice + spread

Created: 2 years ago by: Guest

Jump to the latest result

immutable with concat

direct mutation with splice + spread

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):