Benchmark: [JavaScript] spread operator vs Object.assign - performance test

Tests:

Using spread operator
const firstObject = { stringData: 'foo' }; const secondObject = { numberData: 9999, boolData: true }; const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { stringData: 'foo' }; const secondObject = { numberData: 9999, boolData: true }; const finalObject = Object.assign({}, firstObject, secondObject);

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

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark compares the performance of two approaches to merge two objects in JavaScript: the spread operator (`...`) and `Object.assign()`.

**What is being compared?**

In the individual test cases, we have:

1. **Using spread operator**: This approach uses the spread operator (`...`) to create a new object by merging two existing objects: `firstObject` and `secondObject`. The syntax looks like this:
```javascript
const finalObject = { ...firstObject, ...secondObject };
```
2. **Using Object.assign()**: This approach uses the `Object.assign()` method to merge two objects. The syntax looks like this:
```javascript
const finalObject = Object.assign({}, firstObject, secondObject);
```
**Pros and Cons of each approach:**

1. **Spread Operator (`...`):**
	* Pros:
		+ Concise and expressive syntax.
		+ No need to explicitly create a new object.
		+ Works well with nested objects.
	* Cons:
		+ Can be slower due to the creation of intermediate arrays.
2. **Object.assign()**:
	* Pros:
		+ Efficient, as it only creates a shallow copy of the source objects.
		+ Works well with large datasets.
	* Cons:
		+ Requires explicitly creating an empty object (`{}`) as the target object.
		+ Can be less readable due to the verbose syntax.

**Library used:**

None explicitly mentioned in the benchmark definition. However, `Object.assign()` is a built-in method in JavaScript.

**Special JS feature or syntax:**

The spread operator (`...`) is a relatively recent addition to JavaScript (introduced in ECMAScript 2018), and it's not widely supported in older browsers or environments.

**Other alternatives:**

1. **Lodash's `merge()` function**: This is an alternative implementation of the merge operation, which can be used with the spread operator or `Object.assign()`.
2. **Using `Array.prototype.reduce()`**: Another approach to merging objects using a reducer function.
3. **Manual loop-based merging**: A low-level approach that uses explicit loops to iterate through object properties and assign values.

Keep in mind that these alternative approaches might not be as concise or readable as the spread operator or `Object.assign()`, but they can provide more control over the merge process.

In summary, this benchmark compares two popular ways to merge objects in JavaScript: the spread operator (`...`) and `Object.assign()`. While the spread operator has a concise syntax, it might incur performance penalties due to intermediate array creation. `Object.assign()` is efficient but requires explicit object creation, making it more verbose.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36

Browser/OS: Chrome 104 on Windows

View result in a separate tab

Test name	Executions per second
Using spread operator	843156.1 Ops/sec
Using Object.assign	2450336.0 Ops/sec

Related benchmarks:

[JavaScript] spread operator vs Object.assign - performance test (version: 0)

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

Created: 2 years ago by: Guest

Jump to the latest result

Using spread operator

Using Object.assign

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):