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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

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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I'll break down the benchmark and explain what's being tested, compared, and the pros/cons of each approach.

**What's being tested?**

MeasureThat.net is testing the performance difference between two approaches to merge objects in JavaScript:

1. **Object.assign()**: a built-in method that takes multiple arguments and merges their properties into a new object.
2. **Spread operator (ES6)**: an operator (`...`) that allows you to spread the properties of an object onto another object.

**Options compared**

The benchmark is comparing the performance of these two approaches:

* `Object.assign()` with three additional arguments: `window`, `document`, and `document.body`.
* The spread operator with four additional arguments (again, `window`, `document`, and `document.body`).

**Pros/Cons of each approach**

**Object.assign()**

Pros:

* Wide browser support since it's a built-in method.
* Can be used to merge objects in a predictable way.

Cons:

* May have performance overhead due to the extra function call and argument processing.
* Limited flexibility, as you need to specify all the properties you want to merge explicitly.

**Spread operator**

Pros:

* More concise and expressive way of merging objects.
* Can be more efficient since it avoids the overhead of a function call and argument processing.

Cons:

* May not work in older browsers that don't support ES6 features.
* Can lead to unexpected behavior if not used carefully (e.g., when merging nested objects).

**Library usage**

In this benchmark, `window` and `document` are being treated as properties of the final object. In a real-world scenario, you might want to use these values more judiciously or sanitize them before using them.

**Special JavaScript feature/syntax**

There's no special feature or syntax mentioned in the benchmark. The focus is on comparing two common approaches for merging objects.

**Other alternatives**

If you need to merge objects in a performance-critical part of your code, you might also consider:

* Using libraries like Lodash (specifically, `lodash.merge`) which provides an optimized implementation of object merging.
* Implementing your own custom merge function that takes advantage of browser-specific optimizations or caching.

Keep in mind that the choice of approach ultimately depends on your specific use case, performance requirements, and coding style.

Related benchmarks:

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

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

Created: 3 years ago by: Guest

Jump to the latest result

Using Object.assign

Using the spread operator

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):