Benchmark: `Array.slice(0, N)` vs `Array.length = N` sd434332432

Script Preparation code:

var arr = ["1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","21","22"];

Tests:

`Array.slice(0, N)`
arr = arr.slice(0, 20); console.log(arr);
`Array.length = N`
arr.length = 20; console.log(arr);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
`Array.slice(0, N)`
`Array.length = N`

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36

Browser/OS: Chrome 110 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
`Array.slice(0, N)`	208735.6 Ops/sec
`Array.length = N`	212653.2 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand the benchmark being tested on MeasureThat.net.

**Benchmark Definition**

The benchmark is testing two different approaches for creating an array in JavaScript:

1. `Array.slice(0, N)` (also known as "Slice Method")
2. `arr.length = N` (also known as "Assignment Method")

**Options Compared**

These two options are being compared to determine which one performs better in terms of execution speed.

**Pros and Cons of Each Approach:**

1. **Array.slice(0, N)**:
	* Pros:
		+ Creates a new array with the specified number of elements.
		+ Returns an array with the requested length.
	* Cons:
		+ Can be slower due to the overhead of creating a new array.
		+ May not be as efficient in modern browsers that have optimized `slice()` implementation.
2. **arr.length = N**:
	* Pros:
		+ More lightweight, as it only updates the length property of an existing array object.
		+ Can be faster for small arrays or when using `push()` method to add elements.
	* Cons:
		+ Creates a new array with the specified number of empty slots, which can be inefficient for large arrays.

**Library and Purpose**

There is no specific library being used in this benchmark. The test cases are designed to demonstrate the performance differences between these two common approaches to creating an array in JavaScript.

**Special JS Feature or Syntax**

None of the test cases use any special JavaScript features or syntax beyond what's standard in modern browsers.

**Other Alternatives**

If you're looking for alternative approaches to create arrays, here are a few:

* Using `Array.from()` method: `arr = Array.from(new Array(N))`
* Using `new Array(N)` and assigning elements individually: `arr = new Array(N); arr.push('value');`
* Using `ArrayConstructor` (a legacy way): `var arr = new Array(0).slice(0, N)`

Keep in mind that the best approach for creating an array depends on your specific use case and performance requirements.

**Benchmark Preparation Code**

The provided script preparation code creates a large array with 21 elements:
```javascript
var arr = [“1”, “2”, “3”, “4”, “5”, “6”, “7”, “8”, “9”, “10”, “11”, “12”, “13”, “14”, “15”, “16”, “17”, “18”, “19”, “20”, “21”];
```
The HTML preparation code is not provided, suggesting that the benchmark is running in a headless or automated testing environment.

Related benchmarks:

`Array.slice(0, N)` vs `Array.length = N` sd434332432 (version: 0)

Comparing performance of: `Array.slice(0, N)` vs `Array.length = N`

Created: one year ago by: Guest

Jump to the latest result

`Array.slice(0, N)`

`Array.length = N`

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):