Benchmark: JavaScript spread operator vs Object.assign performance ( nested objects ) into empty object

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world', nested: { nestedData: "Worlds" } } const secondObject = { moreData: 'foo bar', oneNest: { secondNest: { nestedData: "Hellos" }} } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign into empty object
const firstObject = { sampleData: 'Hello world', nested: { nestedData: "Worlds" } } const secondObject = { moreData: 'foo bar', oneNest: { secondNest: { nestedData: "Hellos" }} } 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 into empty object

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36

Browser/OS: Chrome 128 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Using the spread operator	20791154.0 Ops/sec
Using Object.assign into empty object	8445812.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Definition**

The provided JSON represents a benchmark test that compares the performance of two approaches for merging objects in JavaScript:

1. Using the spread operator (`...`): This approach uses the spread syntax to merge the properties of two objects into a new object.
2. Using `Object.assign()` method: This approach uses the `Object.assign()` method to merge the properties of two objects into a new object.

**Options Compared**

The benchmark test compares the performance of these two approaches in merging nested objects. The specific test cases use:

* Two input objects: `firstObject` and `secondObject`, each with nested properties.
* A final output object (`finalObject`) that is created by merging the two input objects using either approach.

**Pros and Cons**

**Using the Spread Operator (`...`)**

Pros:

* More concise and readable code
* Can be used to merge objects in a more declarative way

Cons:

* May not be supported in older browsers or environments
* Can lead to performance issues if the spread operator is not optimized (e.g., if it involves creating new arrays)

**Using `Object.assign()` Method**

Pros:

* Widely supported across modern browsers and environments
* Optimized for performance, as it uses a native method

Cons:

* Can be less readable or more verbose than the spread operator approach
* May require additional setup or configuration to work correctly with nested objects

**Library Used: None**

There is no specific library used in this benchmark test. Both approaches rely on built-in JavaScript features and methods.

**Special JS Feature/Syntax: Spread Operator (`...`)**

The spread operator is a relatively modern feature introduced in ECMAScript 2015 (ES6). It allows for more concise object merging and array creation, but may not be supported in older browsers or environments. In this benchmark test, the spread operator approach is used to merge nested objects.

**Other Considerations**

When working with nested objects, it's essential to consider performance implications when choosing an approach. The spread operator can lead to performance issues if not optimized properly, while `Object.assign()` method is generally more reliable and optimized for performance.

If you're writing a JavaScript application that needs to handle complex object merging or array creation, consider the trade-offs between conciseness, readability, and performance.

**Alternatives**

Some alternative approaches for merging objects in JavaScript include:

* Using `lodash` library (e.g., `_merge()`) which provides a more concise and readable way to merge objects
* Using a custom implementation with loops or recursive functions
* Using other libraries like `immer` for immutable data structures

Keep in mind that the choice of approach depends on your specific use case, performance requirements, and personal preference.

Related benchmarks:

JavaScript spread operator vs Object.assign performance ( nested objects ) into empty object (version: 0)

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

Created: 3 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign into empty object

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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