Benchmark: Creating arrays with specified length

Script Preparation code:

var size = 15;

Tests:

Array Constructor
const array = new Array(size);
Array.from
const array = Array.from({length: size});
Setting length manually
const array = []; array.length = size;
Inserting a value in the last index
const array = []; array[size - 1] = undefined;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array Constructor
Array.from
Setting length manually
Inserting a value in the last index

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what's being tested in each test case.

**Benchmark Definition**

The provided JSON defines a benchmark for creating arrays with a specified length. The script preparation code sets a variable `size` to 15, which is used as the length of the array to be created. There are four test cases that compare different approaches to create an array with a specific length:

1. **Array Constructor**: Using the `new Array(size)` constructor to create an array.
2. **Array.from**: Using the `Array.from()` method to create an array from an object with a `length` property.
3. **Setting length manually**: Setting the `length` property of an empty array (`[]`) to the desired size.
4. **Inserting a value in the last index**: Assigning a value to the last index of an empty array.

**Pros and Cons of each approach**

1. **Array Constructor**: This method is simple and efficient, as it only requires creating a new array object with the specified length. However, it may not be suitable for very large arrays, as it can lead to memory allocation issues.
2. **Array.from**: Using `Array.from()` can be more efficient than assigning a value to an existing array, especially for large arrays. It also provides more control over the array creation process, but may require additional object creation and parsing steps.
3. **Setting length manually**: This method is simple and straightforward, but it can lead to performance issues if the array size is very large or if many arrays are created with the same size. Additionally, it requires assigning a value to each index of the array, which can be slower than creating an array directly.
4. **Inserting a value in the last index**: This method is inefficient, as it involves iterating over all previous indices and assigning values to create the array. It's more suitable for small arrays or when inserting a single element.

**Library and syntax**

None of the test cases use any specific JavaScript libraries or features beyond the standard language syntax.

**Special JS feature or syntax**

There are no special JS features or syntax used in these benchmark definitions.

**Other alternatives**

If you wanted to test alternative methods for creating arrays, some options could include:

* Using `Array.prototype.push()` and assigning values to the array
* Using a library like Lodash to create an array with a specific length
* Using a specialized array creation function from a library like Underscore.js

Keep in mind that these alternatives may not be relevant for this specific benchmark, but they could be used in other scenarios where different array creation methods are being compared.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36

Browser/OS: Chrome 87 on Windows

View result in a separate tab

Test name	Executions per second
Array Constructor	4008855.2 Ops/sec
Array.from	694161.4 Ops/sec
Setting length manually	4848290.5 Ops/sec
Inserting a value in the last index	3871614.8 Ops/sec

Related benchmarks:

Creating arrays with specified length (version: 0)

Comparing performance of: Array Constructor vs Array.from vs Setting length manually vs Inserting a value in the last index

Created: 3 years ago by: Guest

Jump to the latest result

Array Constructor

Array.from

Setting length manually

Inserting a value in the last index

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):