Benchmark: Array constructor vs literal performance - 100000 items

Script Preparation code:

var n = 100000;

function Person(name, age) {
  this.name = name;
  this.age = age;
}

Tests:

Array constructor - 100000 items
var arr = new Array(n); for (var i = 0; i < n; i++) { arr[i] = new Person(i + '', i); }
Array literal - 100000 items
var arr = []; for (var i = 0; i < n; i++) { arr.push(new Person(i + '', i)); }
Array literal (assign by index) - 100000 items
var arr = []; for (var i = 0; i < n; i++) { arr[i] = new Person(i + '', i); }
Array literal (explicit length) - 100000 items
var arr = []; arr.length = n; for (var i = 0; i < n; i++) { arr[i] = new Person(i + '', i); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array constructor - 100000 items
Array literal - 100000 items
Array literal (assign by index) - 100000 items
Array literal (explicit length) - 100000 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 explain what's being tested, the different approaches compared, their pros and cons, and other considerations.

**Benchmark Overview**

The benchmark measures the performance of creating an array with a custom `Person` object using four different methods:

1. Using the `Array` constructor with explicit length assignment (`Array constructor - 100000 items`)
2. Using the `Array` constructor without explicit length assignment (`Array literal - 100000 items`)
3. Using the `[]` syntax for array creation and assigning elements by index (`Array literal (assign by index) - 100000 items`)
4. Using the `[]` syntax for array creation with explicit length assignment (`Array literal (explicit length) - 100000 items`)

**Methods Comparison**

1. **Array constructor**: This method creates a new array instance and assigns elements to it using the `new Person()` constructor.
	* Pros: Allows for more control over the array's behavior, such as setting initial lengths or properties.
	* Cons: Can be slower due to the overhead of creating a new object instance.
2. **Array literal**: This method creates an empty array and assigns elements to it using the `new Person()` constructor.
	* Pros: Faster than the array constructor since no explicit length assignment is required, and it leverages the optimized array creation process in JavaScript.
	* Cons: May not provide as much control over the array's behavior.
3. **Array literal (assign by index)**: This method creates an empty array and assigns elements to it using the `new Person()` constructor, similar to the previous method.
	* Pros: Similar benefits to the array literal method, with more explicit assignment of elements.
	* Cons: May not be as performant due to the repeated use of the `new Person()` constructor.
4. **Array literal (explicit length)**: This method creates an empty array and assigns a specified number of elements to it using the `new Person()` constructor.
	* Pros: Similar benefits to the previous methods, with more explicit control over element assignment.
	* Cons: May not be as performant due to the repeated use of the `new Person()` constructor.

**Other Considerations**

* **Library usage**: The benchmark uses the `Person` class, which is a custom class that represents an individual. Its purpose is not explicitly stated in the benchmark, but it seems to be used for testing purposes only.
* **Special JavaScript features**: There are no special JavaScript features or syntaxes mentioned in the benchmark.

**Alternatives**

If you were to create similar benchmarks for other array creation methods, you could consider the following alternatives:

* Using `Array.from()` method
* Using `Map` objects with the `set()` method
* Using `Set` objects with the `add()` method
* Using `Buffer` or `TypedArray` constructors

Keep in mind that these alternatives might have different performance characteristics and may not be suitable for all use cases.

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/83.0.4103.116 Safari/537.36

Browser/OS: Chrome 83 on Windows

View result in a separate tab

Test name	Executions per second
Array constructor - 100000 items	25.1 Ops/sec
Array literal - 100000 items	23.0 Ops/sec
Array literal (assign by index) - 100000 items	24.8 Ops/sec
Array literal (explicit length) - 100000 items	26.6 Ops/sec

Related benchmarks:

Array constructor vs literal performance - 100000 items (version: 0)

Comparing performance of: Array constructor - 100000 items vs Array literal - 100000 items vs Array literal (assign by index) - 100000 items vs Array literal (explicit length) - 100000 items

Created: 8 years ago by: Guest

Jump to the latest result

Array constructor - 100000 items

Array literal - 100000 items

Array literal (assign by index) - 100000 items

Array literal (explicit length) - 100000 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):