Benchmark: JavaScript spread operator vs Object.assign performance - 21321321

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, sampleData: secondObject.moreData };
Using Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } firstObject.sampleData = secondObject.moreData

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 JavaScript microbenchmark.

The benchmark is comparing two approaches to merge two objects: using the spread operator (`...`) and using `Object.assign`. The script prepares two sample objects, `firstObject` and `secondObject`, with some data. Then, it defines a third object, `finalObject`, which is expected to have merged data from both `firstObject` and `secondObject`.

Here's what's being tested:

1. Using the spread operator (`...`): This approach uses the spread syntax to merge properties from `firstObject` and `secondObject`. The resulting object has all properties from both objects, with any duplicate keys merged into an array.
2. Using `Object.assign`: This approach uses the `assign()` method to copy properties from `secondObject` into `firstObject`, overwriting any existing properties.

**Pros and Cons:**

1. **Using the spread operator (`...`)**
	* Pros:
		+ Concise and readable syntax
		+ Creates a new object with merged data, preserving original objects
	* Cons:
		+ Can be slower due to object creation and property iteration
		+ May not work as expected in older browsers or environments that don't support spread syntax
2. **Using `Object.assign()`**
	* Pros:
		+ Faster and more efficient than using the spread operator
		+ Works across all browsers and environments
	* Cons:
		+ Requires explicit property iteration, which can lead to errors if not done correctly
		+ Less readable syntax compared to spread operator

**Library and purpose:**

None of these approaches rely on external libraries.

**Special JS feature or syntax:**

The benchmark uses the spread operator (`...`), which is a modern JavaScript feature introduced in ECMAScript 2018 (ES8). This syntax allows for concise object merging by spreading properties from one object into another. Older browsers and environments may not support this syntax, so it's essential to test performance in different contexts.

**Other alternatives:**

There are alternative approaches to merge objects, such as:

1. Using `Array.prototype.reduce()`: This approach iterates over the keys of one object and assigns their values from another object.
2. Using a custom loop with `Object.keys()` and `Object.values()`: This approach manually iterates over the properties of an object and assigns values from another object.

These alternatives may have different performance characteristics and readability compared to the spread operator and `Object.assign()` methods used in this benchmark.

Related benchmarks:

JavaScript spread operator vs Object.assign performance - 21321321 (version: 0)

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

Created: 4 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):