Benchmark: JavaScript spread operator vs Object.assign in new Object performance

Tests:

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

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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Let's break down what's being tested in this benchmark and explain the different approaches, their pros and cons, and other considerations.

**Benchmark Test Case**

The test case is measuring the performance difference between two approaches to merge objects in JavaScript:

1. **Using the spread operator (`...`)**: This approach uses the spread operator to create a new object that includes all properties from both `firstObject` and `secondObject`. The syntax is `{ ...firstObject, ...secondObject }`.
2. **Using `Object.assign()`**: This approach uses the `Object.assign()` method to merge two objects into one. The syntax is `Object.assign({}, firstObject, secondObject)`.

**Pros and Cons**

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

Pros:

* Concise and expressive syntax
* Creates a new object, which can be beneficial for performance if the original objects are large or complex
* Can handle nested objects and arrays

Cons:

* May incur additional overhead due to the creation of a new object
* May not be as efficient as `Object.assign()` in some cases (more on this later)

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

Pros:

* Fast and lightweight, as it only creates a reference to the original objects
* Can handle large or complex data sets efficiently

Cons:

* Less expressive syntax compared to the spread operator
* May not be suitable for handling nested objects and arrays

**Performance Comparison**

The benchmark is testing which approach is faster. The results show that `Object.assign()` outperforms the spread operator in this case, with approximately 2x more executions per second.

**Why `Object.assign()` might be faster**

In JavaScript, when using the spread operator (`...`), a new object is created and then all properties are iterated over to copy them from both objects. This can lead to additional overhead due to the creation of a new object and the iteration process. In contrast, `Object.assign()` only creates a reference to the original objects and copies their values directly into the resulting object.

**Other Considerations**

* **Handling nested objects**: Both approaches work well with nested objects, but if you need to handle complex data structures or large datasets, using `Object.assign()` might be a better choice.
* **Performance in older browsers**: If you're targeting older browsers that may not support modern JavaScript features like the spread operator, using `Object.assign()` might be a safer bet.
* **Library usage**: There is no library mentioned in this benchmark. However, if you were to use a library for object merging or manipulation, it could impact performance and readability.

**Alternatives**

Other alternatives for merging objects include:

1. **`Object.create()`**: This method creates a new object based on an existing object.
2. **`lodash.merge()```**: A utility function from the Lodash library that merges two objects into one.
3. **Custom implementation using `forEach()` or `for...in` loops**: You can also implement your own merge logic using JavaScript's built-in methods.

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

Related benchmarks:

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

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

Created: 4 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

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):