Benchmark: JS array union large arrays - concat vs spread

Tests:

Array concat
const a = ['a','b','c'] const b = [1,2,3,4] const c = a.concat(b)
Array spread
const a = ['a','b','c'] const b = [1,2,3,4] const c = [...a, ...b]
Array concat - large numbers
const a = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','x','y','z','w'] const b = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] const c = a.concat(b)
Array spread - large numbers
const a = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','x','y','z','w'] const b = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] const c = [...a,...b]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array concat
Array spread
Array concat - large numbers
Array spread - large numbers

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Measuring JavaScript performance is a fascinating topic.

**What is tested?**

The provided JSON represents a benchmark test for comparing the performance of two ways to concatenate arrays in JavaScript: `concat()` and spread operator (`...`). The tests are designed to measure which approach is faster for both small and large arrays.

**Options compared**

There are two main options being compared:

1. **Array `concat()` method**: This method creates a new array by concatenating the elements of the original arrays.
2. **Spread operator (`...`)**: This operator creates a new array by spreading the elements of the original arrays.

**Pros and Cons of each approach:**

1. **Array `concat()` method**:
	* Pros:
		+ Well-established method, widely supported across browsers.
		+ Can be used with other methods (e.g., `push()`, `splice()`) to manipulate arrays.
	* Cons:
		+ Creates a new array, which can lead to performance issues for large datasets.
		+ Can be slower than spread operator for very large arrays.
2. **Spread operator (`...`)**:
	* Pros:
		+ More modern and efficient way of concatenating arrays.
		+ Does not create a new array, reducing memory allocation and garbage collection overhead.
	* Cons:
		+ Less widely supported across older browsers (pre-ES6).
		+ May require additional setup or library support for older environments.

**Library usage**

None of the tests seem to use any external libraries. The `concat()` method is a built-in JavaScript function, and the spread operator is a native syntax introduced in ECMAScript 2015 (ES6).

**Special JS features or syntax**

The only notable feature used in this benchmark is the spread operator (`...`), which was introduced in ES6. This allows for more concise and efficient array concatenation.

**Alternative approaches**

Other alternatives to the `concat()` method include:

1. **`push()`**: Adding elements to an existing array using `push()`.
2. **`splice()`**: Modifying an array by adding or removing elements.
3. **`Array.prototype.reduce()`**: Using a reduction function to accumulate elements from two arrays.

Each of these alternatives has its own trade-offs and performance characteristics, which may be worth exploring in the context of this benchmark or other performance-critical scenarios.

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36

Browser/OS: Chrome 74 on Windows

View result in a separate tab

Test name	Executions per second
Array concat	4469293.0 Ops/sec
Array spread	19542788.0 Ops/sec
Array concat - large numbers	3651737.8 Ops/sec
Array spread - large numbers	8008690.5 Ops/sec

Related benchmarks:

JS array union large arrays - concat vs spread (version: 0)

Comparing performance of: Array concat vs Array spread vs Array concat - large numbers vs Array spread - large numbers

Created: 5 years ago by: Guest

Jump to the latest result

Array concat

Array spread

Array concat - large numbers

Array spread - large numbers

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):