Benchmark: Reflect.construct vs new and setPrototypeOf

Script Preparation code:

function A() {}
A.prototype.x = 10;

function B() {
  const a = new A()
  Object.setPrototypeOf(a, B.prototype)
}
B.prototype.y = 11;


function C() {
  const a = Reflect.construct(A, [], C)
}
C.prototype.z = 12;

Tests:

new and setPrototypeOf
new B()
Reflect.construct
new C()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
new and setPrototypeOf
Reflect.construct

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.5 Safari/605.1.15

Browser/OS: Safari 18 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
new and setPrototypeOf	59456628.0 Ops/sec
Reflect.construct	43468056.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark is comparing two ways to create an object in JavaScript:

1. **`new B()`**: This creates a new instance of the `B` function using the `new` keyword, which calls the constructor function (in this case, `B`) with no arguments.
2. **`Reflect.construct(A, [], C)`**: This uses the `Reflect.construct()` method to create an object from the `A` constructor function, passing an empty array as the first argument and the `C` context as the second argument.

**Library**

The library being used here is `Reflect`. `Reflect` is a built-in JavaScript library that provides methods for working with objects, such as setting properties on an object or creating new objects. The `Reflect.construct()` method is part of this library.

**Purpose of `Reflect.construct()`**

In the context of this benchmark, `Reflect.construct()` is used to create an object from a constructor function (in this case, `A`) without invoking it with any arguments. This allows for more flexibility in creating objects, especially when working with inheritance or prototypal inheritance.

**Options being compared**

The two options being compared are:

1. **`new B()`**: Creates a new instance of the `B` function using the `new` keyword.
2. **`Reflect.construct(A, [], C)`**: Uses `Reflect.construct()` to create an object from the `A` constructor function.

**Pros and Cons**

* **`new B()`**:
	+ Pros: Easy to use, widely supported, and efficient in most cases.
	+ Cons: May not work as expected when dealing with complex inheritance or prototypal inheritance scenarios.
* **`Reflect.construct(A, [], C)`**:
	+ Pros: Provides more control over object creation, can be useful in certain inheritance scenarios, and is a built-in JavaScript method.
	+ Cons: Less widely supported than `new`, may require additional setup or understanding of the `Reflect` library.

**Other considerations**

* **Performance**: The performance difference between these two methods may be small for simple use cases, but it's still worth considering when working with large datasets or performance-critical applications.
* **Readability and maintainability**: The choice between `new B()` and `Reflect.construct(A, [], C)` can impact code readability and maintainability. `new` is often more straightforward to read, while `Reflect.construct()` may require additional explanation.

**Alternatives**

Other alternatives for creating objects in JavaScript include:

* Using a constructor function with an empty array as the first argument (e.g., `const obj = new A();`)
* Using the `Object.create()` method to create an object from another object or context (e.g., `const obj = Object.create(C.prototype);`)

These alternatives may offer different trade-offs in terms of performance, readability, and maintainability.

Related benchmarks:

Reflect.construct vs new and setPrototypeOf (version: 0)

Comparing performance of: new and setPrototypeOf vs Reflect.construct

Created: 3 years ago by: Guest

Jump to the latest result

new and setPrototypeOf

Reflect.construct

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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