Benchmark: Spread vs Concat Array

Script Preparation code:

var k =[1,2];
var m = [5];

Tests:

concat
var n = k.concat(m)
spread
var n = [...k, ...m]

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: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36

Browser/OS: Chrome 81 on Windows

View result in a separate tab

Test name	Executions per second
concat	2783280.2 Ops/sec
spread	4650483.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition JSON**

The benchmark is designed to compare two approaches to concatenating arrays in JavaScript: `concat()` and spread syntax (`...`).

* **Script Preparation Code**: The script initializes two variables, `k` and `m`, with values `[1, 2]` and `[5]`, respectively. This code is executed before each test case.
* **Html Preparation Code**: There is no HTML preparation code provided.

**Test Cases**

There are two individual test cases:

1. **concat**: Creates a new array `n` by concatenating the arrays `k` and `m` using the `concat()` method.
2. **spread**: Creates a new array `n` by spreading the elements of `k` and `m` using the spread syntax (`...`) and then concatenating them.

**Comparison**

The benchmark is designed to compare the performance of these two approaches on modern JavaScript engines, specifically Chrome 81 running on Windows Desktop.

**Pros and Cons of Each Approach:**

* **concat()**:
	+ Pros:
		- Widely supported and well-known method for concatenation.
		- May be faster due to its native implementation in the browser engine.
	+ Cons:
		- Can lead to performance issues if used excessively, as it creates a new array object on each call.
* **Spread Syntax (`...`)**:
	+ Pros:
		- More concise and readable than `concat()`.
		- Often faster due to its optimized implementation in modern browsers.
	+ Cons:
		- May not be supported by older JavaScript engines or environments.

**Other Considerations:**

* The benchmark assumes that the input arrays are of sufficient size to trigger noticeable performance differences. In reality, smaller arrays may not exhibit significant performance variations between these two approaches.
* This benchmark does not consider other factors like memory allocation, garbage collection, or caching effects, which can impact performance in more complex scenarios.

**Library and Special JS Features:**

There is no library mentioned in the provided benchmark. However, the spread syntax (`...`) relies on a feature introduced in ECMAScript 2015 (ES6), which may not be supported by older browsers or environments.

**Alternatives:**

Other approaches to concatenating arrays include:

* Using `Array.prototype.push()`: Instead of concatenating two arrays, you can add elements one by one using `push()`. This approach can be more efficient if the arrays are relatively small.
* Using a custom implementation with loops: You can write a simple loop to concatenate two arrays manually. This approach might be faster for very large arrays but requires more code and is less readable.

Keep in mind that these alternatives may not provide the same level of performance or readability as the `concat()` method or spread syntax, depending on your specific use case and requirements.

Related benchmarks:

Spread vs Concat Array (version: 0)

Comparing performance of: concat vs spread

Created: 4 years ago by: Registered User

Jump to the latest result

concat

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):