Benchmark: JavaScript spread operator check

Script Preparation code:

const obj1 = { a: "a" };
const obj2 = { b: "b" };

window.obj1 = obj1;
window.obj2 = obj2;

Tests:

Using the spread operator
const finalObject = { c: "a", ...obj1, ...obj2 };
Using direct assignment
const finalObject = { c: "a" } finalObject.a = obj1.a finalObject.b = obj2.b

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using the spread operator
Using direct assignment

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

Browser/OS: Chrome 122 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Using the spread operator	6859493.5 Ops/sec
Using direct assignment	8469316.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this JavaScript benchmark.

**Benchmark Definition**

The benchmark is designed to measure the performance difference between two approaches:

1. Using the spread operator (`...`) to merge objects
2. Direct assignment of individual properties to create a new object

**Options Compared**

We have two options being compared:

* **Using the spread operator**: This approach uses the spread operator (`...`) to merge `obj1` and `obj2` into a single object, `finalObject`. The syntax for this is: `{ ...obj1, ...obj2 }`
* **Direct assignment**: This approach assigns individual properties from `obj1` and `obj2` directly to `finalObject`, like so: `finalObject.a = obj1.a; finalObject.b = obj2.b`

**Pros and Cons**

**Using the spread operator:**

Pros:

* Concise and readable syntax
* Less prone to errors due to explicit merging of properties

Cons:

* Might be slower due to additional object creation and merging

**Direct assignment:**

Pros:

* Fast and lightweight, as only individual properties need to be assigned
* Easy to understand for developers familiar with direct property assignments

Cons:

* More verbose syntax, potentially leading to errors if not done correctly
* Less readable than the spread operator approach

**Other Considerations**

Both approaches have their trade-offs in terms of performance and readability. The spread operator approach is generally considered more modern and concise, but might incur a slight performance penalty due to object creation and merging.

**Library Used**

The benchmark uses the `window` object to assign variables `obj1` and `obj2` as global variables. This is likely done for simplicity and ease of use in the test case.

**Special JS Feature or Syntax**

This benchmark does not rely on any special JavaScript features or syntax beyond what's considered standard at this point (ES6+). If you were to add a feature like `const` declarations, arrow functions, or async/await, it might impact the benchmark results. However, since the test cases are relatively simple, these features do not appear to be relevant here.

**Alternatives**

Other alternatives for creating objects with merged properties could include:

* Using the `Object.assign()` method: `finalObject = Object.assign({}, obj1, obj2)`
* Using a library like Lodash, which provides a `merge` function for merging objects
* Using a template literal or string interpolation to build the final object

Related benchmarks:

JavaScript spread operator check (version: 0)

Comparing performance of: Using the spread operator vs Using direct assignment

Created: 2 years ago by: Guest

Jump to the latest result

Using the spread operator

Using direct assignment

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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