Benchmark: Array concat vs spread operator [2]

Script Preparation code:

random = () => Array(50).fill(Math.floor(Math.random() * 9))

Tests:

Array.prototype.concat
const arr1 = random(); const arr2 = random(); const other = arr1.concat(arr2);
spread operator
const arr1 = random(); const arr2 = random(); const other = [ ...arr1, ...arr2]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.concat
spread operator

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/84.0.4147.105 Safari/537.36 Edg/84.0.522.49

Browser/OS: Chrome 84 on Windows

View result in a separate tab

Test name	Executions per second
Array.prototype.concat	389387.5 Ops/sec
spread operator	358193.9 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the benchmark and explain what's being tested, the options compared, their pros and cons, and other considerations.

**What is being tested?**

The provided JSON represents two test cases for comparing the performance of the `Array.prototype.concat` method with the new ES6 spread operator (`...`). The benchmark is designed to measure which approach is faster in JavaScript.

**Options compared:**

1. **Traditional `concat()` method**: This is a built-in Array method that concatenates two or more arrays and returns a new array.
2. **New ES6 spread operator (`...`)**: This operator allows you to expand an iterable (such as an array) into individual elements.

**Pros and Cons of each approach:**

1. **Traditional `concat()` method**:
	* Pros:
		+ Widely supported and well-established.
		+ Easy to understand and use, especially for developers familiar with older JavaScript versions.
	* Cons:
		+ Creates a new array, which can lead to increased memory usage.
		+ Can be slower than the spread operator due to the overhead of concatenating arrays.
2. **New ES6 spread operator (`...`)**:
	* Pros:
		+ More efficient than `concat()` as it avoids creating a new array and uses the existing one's length and index information.
		+ Often faster, especially for larger arrays.
	* Cons:
		+ Requires support for the newer syntax, which might not be available in older browsers or versions of JavaScript.
		+ Can be less intuitive for developers who are not familiar with this syntax.

**Library used:**

In neither of the test cases is a library explicitly mentioned. However, it's likely that the benchmark uses an engine like V8 (used by Google Chrome) or SpiderMonkey (used by Mozilla Firefox) to execute the JavaScript code.

**Special JS feature or syntax:**

There are no special features or syntaxes used in this benchmark that would require specific knowledge of advanced JavaScript topics. The benchmark focuses on comparing two well-known and widely supported methods for concatenating arrays.

**Other alternatives:**

If you're interested in exploring alternative methods for array concatenation, here are a few examples:

1. `Array.prototype.push()`: This method can be used to append elements to an array, but it's not the most efficient way to concatenate two arrays.
2. `reduce()`: Some developers use `reduce()` with the initial value set to an empty array and accumulate the concatenation process, which can also lead to performance issues.

Keep in mind that these alternatives might not be as optimized or well-supported as the traditional `concat()` method or the spread operator.

In summary, the benchmark is designed to measure the performance difference between two common methods for concatenating arrays in JavaScript: the traditional `concat()` method and the new ES6 spread operator (`...`). The results can help developers understand which approach is more efficient and make informed decisions about code optimization.

Related benchmarks:

Array concat vs spread operator [2] (version: 0)

Compare the new ES6 spread operator with the traditional concat() method

Comparing performance of: Array.prototype.concat vs spread operator

Created: 4 years ago by: Guest

Jump to the latest result

Array.prototype.concat

spread operator

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):