Benchmark: joining two arrays with concat and slice

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

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36

Browser/OS: Chrome 87 on Linux

View result in a separate tab

Test name	Executions per second
immutable with concat	3062459.5 Ops/sec
direct mutation with splice + spread	3755075.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks to measure the performance of different approaches.

The provided JSON represents two benchmark test cases:

1. **Joining two arrays with `concat`**: This test case creates two identical arrays, `a` and `b`, containing 24 "hello" strings. The benchmark then uses the `concat()` method to merge these two arrays into a single array called `other`. The test case measures the performance of this operation.
2. **Direct mutation with `splice` + spread**: This test case creates an identical array, `a`, as in the previous test case. However, instead of using `concat()`, it uses the `splice()` method to mutate the original array `a` by removing its existing elements and adding new ones using the spread operator (`...b`). The test case measures the performance of this operation.

**Options Compared**

The two test cases compare the performance of:

* Using `concat()` to merge arrays, which creates a new array object.
* Directly mutating an original array using `splice()`, followed by spreading the new elements into the array using the spread operator (`...`).

**Pros and Cons of Each Approach**

1. **Using `concat()`**
	* Pros:
		+ Creates a new, immutable array that cannot be modified directly.
		+ Does not modify the original arrays.
	* Cons:
		+ Creates an additional array object in memory, which can lead to increased memory usage.
		+ May incur additional overhead due to array creation and copying.
2. **Direct mutation with `splice` + spread**
	* Pros:
		+ Modifies the original array directly without creating a new one.
		+ Does not create an additional array object in memory.
	* Cons:
		+ Mutates the original array, which may be undesirable if the array is intended to remain unchanged.
		+ May incur additional overhead due to array modification and copying.

**Library Usage**

In this benchmark, no specific JavaScript library is used. The `concat()` method is a built-in method of arrays in JavaScript, while the `splice()` method and spread operator (`...`) are also part of the standard language.

**Special JS Features or Syntax**

The only special feature used in these test cases is the use of spread syntax (`...b`), which is a relatively recent addition to the JavaScript language (introduced in ECMAScript 2015). This allows for concise array creation and assignment.

Related benchmarks:

joining two arrays with concat and slice (version: 0)

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

Created: 3 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 2 months ago):