Benchmark: JavaScript spread operator vs Object.assign performance

Tests:

...
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = Object.assign({}, firstObject, secondObject);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
...
Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided JSON and explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**
The benchmark is to compare the performance of two approaches:

1. Using the JavaScript spread operator (`...`) to merge objects.
2. Using the `Object.assign()` method to merge objects.

**Benchmark Preparation Code**
There is no preparation code provided for the benchmark.

**Individual Test Cases**
There are two test cases:

1. **Test Case 1: Using the JavaScript spread operator**
The script defines three objects:
	* `firstObject` with a property `sampleData` set to `'Hello world'`.
	* `secondObject` with a property `moreData` set to `'foo bar'`.
	* The final object is created by spreading `firstObject` and `secondObject` using the spread operator (`...`).
2. **Test Case 2: Using `Object.assign()**`
The script defines three objects:
	* `firstObject` with a property `sampleData` set to `'Hello world'`.
	* `secondObject` with a property `moreData` set to `'foo bar'`.
	* The final object is created by calling `Object.assign()` and passing an empty object (`{}`), followed by `firstObject` and then `secondObject`.

**What's being tested?**
The benchmark measures the performance of merging two objects using either the spread operator or `Object.assign()`.

**Pros and Cons**

* **Using the JavaScript spread operator:**
	+ Pros:
		- More readable and concise code.
		- No need to specify the properties you want to merge from each object.
	+ Cons:
		- May be slower due to the overhead of parsing the spread operator.
		- Not all browsers support the spread operator (e.g., older versions of Internet Explorer).
* **Using `Object.assign()`:**
	+ Pros:
		- Widely supported across modern browsers and Node.js environments.
		- Can be faster for large objects or complex merges, as it avoids the overhead of parsing the spread operator.
	+ Cons:
		- Requires specifying each property to merge from each object using an array of key-value pairs.
		- Less readable code.

**Library: None**

There are no external libraries used in this benchmark.

**Special JS feature or syntax:**
The JavaScript spread operator (`...`) is a relatively recent addition to the language, introduced in ECMAScript 2018 (ES2018). It allows you to merge objects by spreading their properties into an object. This feature was not widely supported until ES2019, but it's now included in most modern browsers and Node.js environments.

**Other alternatives:**
If you need to merge objects without using the spread operator or `Object.assign()`, other approaches include:

1. Using `Array.prototype.concat()` to concatenate arrays of key-value pairs from each object.
2. Writing a custom function to iterate over the properties of one object and assign values from another object.

However, these alternatives are generally less readable and may not be as efficient as using the spread operator or `Object.assign()`.

Related benchmarks:

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

Comparing performance of: ... vs Object.assign

Created: 3 years ago by: Registered User

Jump to the latest result

...

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):