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

Tests:

immutable with concat
var a = [ "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello" ] var b = [ "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello" ] var other = a.concat(b)
direct mutation with splice + spread
var a = [ "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello" ] var b = [ "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello" ] a.splice(a.length, 0, ...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 one month ago):

LLMs can make mistakes. Check important info.

**Overview**

The provided JSON represents a benchmark test case on MeasureThat.net, which compares the performance of two approaches for joining two arrays in JavaScript: using `Array.prototype.concat()` and using the `splice()` method with the spread operator (`...`).

**What is being tested?**

In this benchmark, two identical arrays, `a` and `b`, are created and then used to join each other using one of two methods:

1. **Immutable with `concat()`**: The `concat()` method returns a new array that is the result of joining the elements of `a` and `b`. This approach does not modify the original arrays.
2. **Direct mutation with `splice()` + spread**: Instead of using `concat()`, the `splice()` method is used to insert all elements of `b` at the end of `a`, without modifying `a`.

**Options compared**

The two options being tested are:

1. **Immutable with `concat()`**
2. **Direct mutation with `splice()` + spread**

**Pros and Cons of each approach:**

1. **Immutable with `concat()`**
	* Pros:
		+ Does not modify the original arrays, which can be beneficial for data integrity and thread safety.
		+ Can be more predictable and easier to reason about, as it does not involve modifying the array in-place.
	* Cons:
		+ Creates a new array, which can result in additional memory allocation and garbage collection overhead.
2. **Direct mutation with `splice()` + spread**
	* Pros:
		+ Does not create a new array, which can reduce memory allocation and garbage collection overhead.
	* Cons:
		+ Modifies the original array, which can lead to unexpected behavior if the original array is being used elsewhere.
		+ Can be less predictable and more error-prone, as it involves modifying the array in-place.

**Library: None**

There are no external libraries used in this benchmark. The test cases only use built-in JavaScript methods (`concat()`, `splice()`) and syntax features (spread operator).

**Special JS feature or syntax:**

None of the tested approaches rely on any special JavaScript features or syntax beyond what is normally available in the language.

**Other alternatives**

There are alternative ways to join two arrays in JavaScript, such as using `Array.prototype.reduce()` or `Array.prototype.forEach()`, but these methods may not be directly comparable to `concat()` and `splice()` in terms of performance. Other approaches might involve using libraries like Lodash or Underscore.js, which provide utility functions for array manipulation.

Keep in mind that the choice of approach depends on the specific use case, data size, and performance requirements. This benchmark provides a simple comparison between two common methods, but real-world scenarios may require more nuanced evaluation.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.134 Safari/537.36

Browser/OS: Chrome 103 on Windows

View result in a separate tab

Test name	Executions per second
immutable with concat	6084274.5 Ops/sec
direct mutation with splice + spread	3636615.8 Ops/sec

Related benchmarks:

Array.prototype.concat vs splice for joining two arrays fix (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 one month ago):