Benchmark: Array constructor vs literal performance (10 items)

Tests:

Array constructor - 10 items
var n = 10; var arr = new Array(n); for (var i = 0; i < n; i++) { arr[i] = i; }
Array literal - 10 items
var n = 10; var arr = []; for (var i = 0; i < n; i++) { arr.push(i); }
Array literal (assign by index) - 10 items
var n = 10; var arr = []; for (var i = 0; i < n; i++) { arr[i] = i; }
Array literal (explicit length) - 10 items
var n = 10; var arr = []; arr.length = n; for (var i = 0; i < n; i++) { arr[i] = i; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array constructor - 10 items
Array literal - 10 items
Array literal (assign by index) - 10 items
Array literal (explicit length) - 10 items

Fastest: N/A

Slowest: N/A

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 its options.

**Benchmark Overview**

The test case measures the performance of different approaches to create an array in JavaScript:

1. Using the `Array` constructor with explicit length (`new Array(n)`).
2. Using the literal syntax with a fixed length (e.g., `[]` and then setting `length = n`).
3. Using the literal syntax without specifying a fixed length (e.g., `[]` and using `push` to add elements).

**Benchmark Definitions**

There are four test cases:

1. **Array constructor - 10 items**: Creates an array with explicit length using `new Array(n)`.
2. **Array literal - 10 items**: Creates an array with a fixed length using `[]` and then setting `length = n`.
3. **Array literal (assign by index) - 10 items**: Similar to the previous test case, but instead of setting `length`, it uses `push` to add elements.
4. **Array literal (explicit length) - 10 items**: Creates an array with a fixed length using `[]` and then setting `length = n`.

**Options Compared**

The benchmark compares the performance of three approaches:

1. **Explicit Length**: Using `new Array(n)` or `[]` followed by `length = n`.
2. **Push-based**: Using `[]` and adding elements using `push`, like in test case 3.
3. **Literal with Explicit Length**: Similar to explicit length, but uses a literal syntax (e.g., `[...]`) instead of `new Array(n)`.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **Explicit Length**:
	* Pros: Can be more efficient, especially when dealing with large arrays.
	* Cons: May lead to issues if the length is not set correctly.
2. **Push-based**:
	* Pros: More flexible, as it allows adding elements dynamically without having to specify a fixed length.
	* Cons: May be slower due to the repeated calls to `push`.
3. **Literal with Explicit Length**:
	* Pros: A balance between efficiency and flexibility.
	* Cons: May not be as efficient as explicit length for very large arrays.

**Library and Special JS Features**

There are no notable libraries or special JS features mentioned in the benchmark definitions.

**Other Alternatives**

If you're interested in exploring alternative approaches, consider the following:

1. **Using `Array.from()`**: A more modern approach to creating arrays from scratch.
2. **Using a library like Lodash's `createArray()` function**: Can provide additional flexibility and features.
3. **Using a different array creation syntax**, such as using `Map` or `Set`.

Keep in mind that the performance differences between these approaches may vary depending on the specific use case and JavaScript engine being used.

In summary, this benchmark provides a useful comparison of three common approaches to creating arrays in JavaScript, highlighting their pros and cons. The choice of approach ultimately depends on your specific requirements and preferences.

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Windows

View result in a separate tab

Test name	Executions per second
Array constructor - 10 items	8112736.0 Ops/sec
Array literal - 10 items	31976448.0 Ops/sec
Array literal (assign by index) - 10 items	26319300.0 Ops/sec
Array literal (explicit length) - 10 items	10709304.0 Ops/sec

Related benchmarks:

Array constructor vs literal performance (10 items) (version: 0)

Comparing performance of: Array constructor - 10 items vs Array literal - 10 items vs Array literal (assign by index) - 10 items vs Array literal (explicit length) - 10 items

Created: 8 years ago by: Registered User

Jump to the latest result

Array constructor - 10 items

Array literal - 10 items

Array literal (assign by index) - 10 items

Array literal (explicit length) - 10 items

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):