Benchmark: Array.slice vs manual clone

Script Preparation code:

var arr=(function(){
	var arr=[];
	for(var i=0; i<80000; i++){
		arr.push(i);
    }
	return arr;
}())

Tests:

Array.slice
var arr2=arr.slice(); return arr2;
Manual copy
var arr3=new Array(arr.length); for(var i=0; i<arr.length; i++){ arr3[i]=arr[i]; } return arr3;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.slice
Manual copy

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36

Browser/OS: Chrome 105 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Array.slice	40920.8 Ops/sec
Manual copy	185.5 Ops/sec

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

LLMs can make mistakes. Check important info.

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

The benchmark is comparing two approaches to creating a new array from an existing one:

1. `Array.slice()`
2. Manual cloning using the `new Array()` constructor.

**What are we testing?**

We're testing which approach is faster, more efficient, and has better performance in terms of execution speed.

**Options compared:**

* **`Array.slice()`**: This method creates a shallow copy of a portion of an array. It returns a new array object with references to the same elements as the original array.
* **Manual cloning using `new Array()`**: This approach creates a completely new array, element by element, by assigning each element from the original array to the corresponding index in the new array.

**Pros and Cons:**

* **`Array.slice()`**:
	+ Pros:
		- Creates a shallow copy of a portion of an array, which can be useful when you need to modify only part of the original array.
		- Can be faster than manual cloning because it avoids creating unnecessary objects.
	+ Cons:
		- May not work correctly for arrays with complex data structures (e.g., arrays containing other arrays or objects).
		- Can cause issues if the resulting slice is modified, as it will affect the original array.
* **Manual cloning using `new Array()`**:
	+ Pros:
		- Creates a completely new array with no references to the original array.
		- Ensures that modifying the cloned array does not affect the original array.
	+ Cons:
		- Can be slower than `Array.slice()` because it involves creating unnecessary objects.
		- Requires more code and may be less readable.

**Library:**

There is no specific library being used in this benchmark. The `Array.slice()` method is a built-in JavaScript function, while the manual cloning approach uses only the `new Array()` constructor and basic syntax.

**Special JS feature or syntax:**

The benchmark does not use any special JavaScript features or syntax beyond what's considered standard in modern JavaScript (ES6+). It uses only the basic syntax for creating arrays and assigning elements to them.

**Other alternatives:**

If you need a more complex cloning approach, other alternatives might include:

* `Array.prototype.map()`: Creates a new array with the same number of elements as the original array, but with each element transformed according to the provided function.
* `Array.prototype.filter()`: Creates a new array with only the elements that pass the test implemented by the provided function.
* Using `JSON.parse(JSON.stringify())` (although this is not recommended due to its performance and potential issues).

In summary, the benchmark is testing two approaches to creating a new array from an existing one: using `Array.slice()` or manual cloning using `new Array()`. The results can help you decide which approach to use depending on your specific needs.

Related benchmarks:

Array.slice vs manual clone (version: 0)

Comparing performance of: Array.slice vs Manual copy

Created: 2 years ago by: Guest

Jump to the latest result

Array.slice

Manual copy

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):