Benchmark: JavaScript spread operator vs Object.assign performance vs Loop

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world', sampleData2: 'Hello world' } const secondObject = { moreData: 'foo bar', moreData2: 'foo bar'} const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { sampleData: 'Hello world', sampleData2: 'Hello world' } const secondObject = { moreData: 'foo bar', moreData2: 'foo bar'} const finalObject = Object.assign(firstObject, secondObject);
Using a loop
const firstObject = { sampleData: 'Hello world', sampleData2: 'Hello world' } const secondObject = { moreData: 'foo bar', moreData2: 'foo bar'} const finalObject = {}; for (const key in firstObject) { finalObject[key] = firstObject[key] } for (const key in secondObject) { finalObject[key] = secondObject[key] }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using the spread operator
Using Object.assign
Using a loop

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 benchmark definition and test cases.

**What is tested:**

The benchmark tests the performance of three different approaches to merge two objects in JavaScript:

1. Using the spread operator (`...`)
2. Using `Object.assign()`
3. Using a loop with `for...in` iteration

These three approaches are compared to determine which one performs the best.

**Options comparison:**

Here's a brief overview of each approach and their pros/cons:

1. **Using the spread operator (`...`)**
	* Pros:
		+ Concise and readable syntax
		+ Can handle nested objects
	* Cons:
		+ May incur overhead due to function call and object creation
2. **Using `Object.assign()`**
	* Pros:
		+ Well-established and widely supported API
		+ Can handle nested objects
	* Cons:
		+ May be slower than other methods, especially for large objects
3. **Using a loop with `for...in` iteration**
	* Pros:
		+ Low overhead, as it only iterates over the object's properties
	* Cons:
		+ Requires explicit property iteration, which can be error-prone

**Library and special JS features:**

In this benchmark, no specific library is used. However, the `Object.assign()` method relies on the ECMAScript 2015 (`ES6`) standard, which introduced the spread operator as a part of the language.

**Considerations:**

* The use of `Object.assign()` may be slower due to its overhead and potential caching issues.
* The spread operator's performance is sensitive to the object size and nesting level. For very large objects or deeply nested structures, other methods might be more efficient.
* Looping over properties can lead to errors if not implemented correctly.

**Other alternatives:**

Some alternative approaches for merging two objects in JavaScript include:

1. Using `lodash.merge()`: A popular utility library that provides a robust implementation of object merging.
2. Using `mergeDeep()` from the `lodash-es` library: An ES6 module version of `lodash.merge()`, designed specifically for deep object merges.
3. Implementing custom object merge logic using recursion or iteration.

Keep in mind that these alternatives might introduce additional dependencies or performance overhead, depending on your specific use case.

**Benchmark result interpretation:**

The provided benchmark results show the executions per second (ExecutionsPerSecond) for each test case:

* "Using a loop" is the fastest approach.
* "Using Object.assign()" is slower than the spread operator and loop but still faster than a custom implementation.
* "Using the spread operator" has performance similar to the loop, indicating that its overhead may be negligible in this specific benchmark.

Related benchmarks:

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

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

Created: 4 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

Using a loop

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):