Benchmark: JavaScript spread operator vs Object.assign performance for two targets

Tests:

Using the spread operator
const config1= {x:1, y:2}; const config2= {a:3, b:4}; const unique = Object.keys(Object.assign({}, config1, config2));
Using Object.assign
const config1= {x:1, y:2}; const config2= {a:3, b:4}; const unique = Object.keys({...config1, ...config2})

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

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared options, pros and cons, library usage, and other considerations.

**Benchmark Overview**

The benchmark measures the performance difference between using the JavaScript spread operator (`...`) versus `Object.assign` when combining two objects to create a unique set of keys.

**Test Cases**

There are two test cases:

1. **Using the Spread Operator**: The benchmark definition is: `const config1= {x:1, y:2};\r\nconst config2= {a:3, b:4};\r\nconst unique = Object.keys(Object.assign({}, config1, config2));`. This code uses the spread operator (`...`) to combine `config1` and `config2`, and then extracts the unique keys using `Object.keys()`.
2. **Using Object.assign**: The benchmark definition is: `const config1= {x:1, y:2};\r\nconst config2= {a:3, b:4};\r\nconst unique = Object.keys({...config1, ...config2})`. This code uses `Object.assign()` to merge `config1` and `config2`, and then extracts the unique keys using `Object.keys()`.

**Comparison**

The benchmark compares the performance of these two approaches:

* **Using Spread Operator**: This approach uses the spread operator (`...`) to combine the objects, which creates a new object with the merged properties. The resulting object is then passed to `Object.keys()`.
* **Using Object.assign**: This approach uses `Object.assign()` to merge the objects, which returns the modified original object. The `Object.keys()` function is then called on this result.

**Pros and Cons**

Here are some pros and cons of each approach:

* **Using Spread Operator**:
	+ Pros: Can be more readable and concise, especially when working with multiple objects.
	+ Cons: May create a new object in memory, which can impact performance if dealing with large datasets.
* **Using Object.assign**:
	+ Pros: Can be faster since it modifies the original object, reducing memory allocation.
	+ Cons: May not be as readable or maintainable for complex merge scenarios.

**Library Usage**

There is no explicit library usage in these test cases. However, `Object.keys()` is a built-in JavaScript function that extracts an array of keys from an object.

**Special JS Features/Syntax**

There are no special JavaScript features or syntaxes used in these benchmark cases.

**Other Considerations**

* The benchmark uses Firefox 110 as the browser, which might not be representative of other browsers' performance.
* The test is run on a desktop platform, which could affect results compared to mobile devices.
* The `ExecutionsPerSecond` metric provides an idea of how fast each approach executes, but it's essential to consider other factors like memory usage and system load.

**Alternatives**

Other alternatives for combining objects in JavaScript include:

1. **Object.create()**: Creates a new object with the specified properties inherited from another object.
2. **Array.prototype.reduce()**: Combines two arrays into one using a reduce callback function.
3. **JSON merge libraries**: There are various libraries available that can be used to merge JSON objects, such as `jsonmerge` or `lodash.merge`.

Keep in mind that each approach has its pros and cons, and the choice of which one to use depends on the specific requirements of your project.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/110.0

Browser/OS: Firefox 110 on Windows

View result in a separate tab

Test name	Executions per second
Using the spread operator	8518512.0 Ops/sec
Using Object.assign	6243275.0 Ops/sec

Related benchmarks:

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

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

Created: one year ago by: Registered User

Jump to the latest result

Using the spread operator

Using Object.assign

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):