Benchmark: JS object spread vs object.assign

Tests:

Using the spread operator
const initialBooks = [ { title: "Unsouled", author: "Will Wight" }, { title: "The Iron Prince", author: "Bryce O'Connor and Luke Chmilenko" }, { title: "He Who Fights with Monsters", author: "Shirtaloon" }, ]; const additionalBook = { title: "Lightbringer", author: "Brent Weeks" }; const allBooks = [ {...initialBooks, ...additionalBook}]
Using Object.assign
const initialBooks = [ { title: "Unsouled", author: "Will Wight" }, { title: "The Iron Prince", author: "Bryce O'Connor and Luke Chmilenko" }, { title: "He Who Fights with Monsters", author: "Shirtaloon" }, ]; const additionalBook = { title: "Lightbringer", author: "Brent Weeks" }; const allBooks = [ Object.assign(initialBooks, additionalBook)]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using the spread operator
Using Object.assign

Fastest: N/A

Slowest: N/A

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

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Let's break down what's being tested in this benchmark.

**Benchmark Definition**

The benchmark is comparing two approaches for creating a new array by concatenating an existing array with a single object:

1. Using the spread operator (`[...initialBooks, ...additionalBook]`)
2. Using `Object.assign()` (`Object.assign(initialBooks, additionalBook)`)

**Options Compared**

Both approaches are being tested to determine which one is faster.

**Pros and Cons of Each Approach:**

**Using the Spread Operator:**

Pros:

* Readable and concise syntax
* Less memory overhead since it only copies the references to the existing array elements

Cons:

* Can be slower than `Object.assign()` due to its implementation details (see below)

**Using Object.assign():**

Pros:

* Generally faster, especially for larger arrays or objects
* More familiar syntax to developers who are used to using `assign` methods in other programming languages

Cons:

* Less readable and more verbose syntax compared to the spread operator
* Can be slower due to its implementation details (see below)

**Implementation Details:**

In V8, the JavaScript engine used by Google Chrome, `Object.assign()` is implemented as a loop that iterates over the properties of the source object and copies them to the target object. This can lead to slower performance for small arrays or objects.

On the other hand, the spread operator (`[...array]`) is implemented using a technique called " array copying with shallow cloning". This involves creating a new array and then iterating over the elements of the original array, copying their values and references to the new array. Since it only copies the references, this approach can be faster than `Object.assign()` for small arrays or objects.

**Library Used**

In neither test case is any external library used. The spread operator and `Object.assign()` are built-in JavaScript features.

**Special JS Feature/Syntax:**

The spread operator (`[...array]`) was introduced in ECMAScript 2015 (ES6) as a new way to create arrays from iterables or spreads. It's a concise and readable syntax that eliminates the need for explicit array concatenation using methods like `push()` or `concat()`.

**Other Alternatives:**

If you're interested in exploring alternative approaches, here are some options:

* Using `Array.prototype.concat()` or `Array.prototype.push()`: These methods can be used to concatenate arrays, but they might not be as readable or efficient as the spread operator or `Object.assign()`.
* Using a library like Lodash's `_.concat()` function: This function provides a more concise and expressive way to concatenate arrays, but it also adds an additional dependency.

In summary, the benchmark is comparing two approaches for creating a new array by concatenating an existing array with a single object. The spread operator and `Object.assign()` are being tested to determine which one is faster. While both have their pros and cons, the spread operator is generally more readable and concise, but might be slower due to its implementation details.

Related benchmarks:

JS object spread vs object.assign (version: 0)

object spread vs assign

Comparing performance of: Using the spread operator vs Using Object.assign

Created: 2 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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