Benchmark: JavaScript spread operator vs immutable Object.assign performance

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Using 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
Using the spread operator
Using 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 what's being tested in this benchmark.

The benchmark is comparing two approaches to merge two objects in JavaScript:

1. **Spread Operator (`...`)**: This syntax was introduced in ECMAScript 2018 (ES2018). It allows you to expand an object literal by spreading its properties onto another object, effectively creating a new object that combines the two.
2. **Immutable `Object.assign()` method**: The `Object.assign()` method is used to copy the values of all enumerable own properties from one or more source objects into a destination object.

**Options Compared:**

* Spread Operator (`...`)
* Immutable `Object.assign()` method

**Pros and Cons of Each Approach:**

1. **Spread Operator (`...`)**:
	* Pros:
		+ More concise and readable syntax.
		+ Less error-prone, as it's harder to accidentally overwrite properties.
	* Cons:
		+ May be slower due to the overhead of creating a new object using `Object.create()` or `Array.prototype.slice()`.
2. **Immutable `Object.assign()` method**:
	* Pros:
		+ Can be faster for large objects, as it uses a single function call with multiple arguments.
	* Cons:
		+ More verbose syntax and prone to errors (e.g., incorrect property ordering).

**Other Considerations:**

* The benchmark doesn't consider the impact of object size or complexity on performance. As mentioned earlier, larger objects might favor `Object.assign()`.
* No consideration is given to browser-specific optimizations or caching mechanisms.

**Library Used:**
No explicit library is used in this benchmark. However, some browsers might use internal libraries or optimized implementations of these APIs.

**Special JS Feature/Syntax:**
None are explicitly mentioned in the provided code snippets.

**Benchmark Preparation Code and JSON:**

The provided `Script Preparation Code` and `Html Preparation Code` are empty, suggesting that the user has not contributed any additional setup or test harness code. The benchmark definitions are stored in a JSON file, which defines the two test cases:

1. "Using the spread operator"
2. "Using Object.assign"

**Benchmark Results:**

The latest benchmark results show that Chrome 68 executes the `Object.assign()` method approximately 34% faster than the spread operator (`...`) for this specific use case.

Keep in mind that these results might not be representative of all browsers or scenarios, as the benchmark's scope is limited to a single browser and test setup.

Related benchmarks:

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

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

Created: 7 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):