Benchmark: JavScript spread operator vs Object.assign

Tests:

Using spread operator
const first = {test: 1}; const second = {hi: 2}; const final = {...first, ...second}
Using Object.assign
const first = {test: 1}; const second = {hi: 2}; const final = Object.assign({}, first, second);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using spread operator
Using Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

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

**What is being tested?**

The provided benchmark compares two approaches for merging objects in JavaScript:

1. Using the spread operator (`{...first, ...second}`)
2. Using `Object.assign()` with an initial object (`const final = Object.assign({}, first, second)`)

**Options compared:**

* **Spread Operator:** This approach uses the syntax `{...obj1, ...obj2}` to merge two objects, `obj1` and `obj2`. It creates a new object that includes all key-value pairs from both objects.
* **Object.assign():** This approach uses the `Object.assign()` method to merge two objects. It takes an initial object (`{}`) as the first argument, followed by one or more source objects.

**Pros and Cons:**

* **Spread Operator:**
	+ Pros:
		- More concise and readable syntax.
		- Creates a new object without modifying the original objects.
	+ Cons:
		- Can be slower due to object creation overhead.
		- May not work correctly if used with `const` or `let` declarations (since it creates a new object reference).
* **Object.assign():**
	+ Pros:
		- Faster than spread operator, since it modifies the initial object directly.
		- Works correctly with `const` and `let` declarations.
	+ Cons:
		- Less concise syntax.
		- Modifies the original object if not used carefully.

**Library:**

None. This benchmark only uses built-in JavaScript features.

**Special JS feature or syntax:**

The spread operator (`{...obj1, ...obj2}`) is a new feature introduced in ECMAScript 2018 (ES10). It allows for more concise and expressive object merging.

**Benchmark preparation code:**

Since the `Script Preparation Code` field is empty, it's assumed that the benchmark script simply defines two objects (`first` and `second`) with some properties, and then uses the spread operator or `Object.assign()` to merge them into a new object (`final`). The exact implementation details are not provided.

**Other alternatives:**

* **Using the `Object.create()` method:** This approach creates a new object using the `Object.create()` method, followed by assigning values from the source objects using `Object.assign()`.
```javascript
const final = Object.create(Object.getPrototypeOf(first));
final.test = first.test;
final.hi = second.hi;
```
* **Using the `reduce()` method:** This approach uses the `reduce()` method to accumulate properties from both objects into a new object.
```javascript
const final = {};
Object.keys(first).forEach(key => final[key] = first[key]);
Object.keys(second).forEach(key => final[key] = second[key]);
```
These alternatives are less common and may not be as concise or readable as the spread operator or `Object.assign()`.

Related benchmarks:

JavScript spread operator vs Object.assign (version: 0)

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

Created: 8 years ago by: Guest

Jump to the latest result

Using 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):