Benchmark: JavaScript spread operator vs Object.assign 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' } function newState(a, b) { return Object.assign({}, a, b); } const finalObject = newState(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 llama3.1:latest, generated one year ago):

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Let's dive into the details of this benchmark test.

**Benchmark Description**

The benchmark is testing the performance difference between two ways to merge two objects in JavaScript: using the spread operator (`...`) and using `Object.assign()`.

**Test Case 1: Using the Spread Operator**

In this test case, we have two objects:

```javascript
const firstObject = { sampleData: 'Hello world' };
const secondObject = { moreData: 'foo bar' };
```

The benchmark creates a new object by using the spread operator to merge these two objects:

```javascript
const finalObject = { ...firstObject, ...secondObject };
```

**Test Case 2: Using Object.assign()**

In this test case, we have the same two objects as above. However, instead of using the spread operator, the benchmark defines a function `newState()` that takes two arguments (`a` and `b`) and returns a new object by merging them using `Object.assign()`:

```javascript
function newState(a, b) {
  return Object.assign({}, a, b);
}

const finalObject = newState(firstObject, secondObject);
```

**Benchmark Results**

The latest benchmark results show that the test running with `Object.assign()` performs at approximately 3624 executions per second on Firefox 60. In contrast, the test using the spread operator (`...`) runs at around 2426 executions per second.

**Comparison of Options**

Here's a comparison of the pros and cons of these two approaches:

* **Spread Operator (`...`)**:
	+ Pros: Concise syntax, easy to read and write.
	+ Cons: May be slower than `Object.assign()` due to its dynamic nature (more overhead).
* **Object.assign()**:
	+ Pros: Generally faster than the spread operator, as it's a more efficient method for merging objects.
	+ Cons: More verbose code, potentially harder to read.

**Other Considerations**

When choosing between these two methods, consider the following factors:

1. **Performance-critical code**: If you're working on performance-critical sections of your codebase, using `Object.assign()` might be a better choice due to its generally faster execution speed.
2. **Code readability and maintainability**: In cases where code readability and maintainability are more important than raw performance, the spread operator (`...`) is often a better option due to its concise syntax.

**Library Used (None)**

No external libraries or frameworks are used in this benchmark test.

**Special JS Feature or Syntax (Spread Operator (`...`))**

The benchmark uses the spread operator (`...`) as the primary way to merge objects in Test Case 1. The spread operator is a JavaScript feature that allows you to easily create new arrays or objects by spreading an existing array or object's elements into a new one.

**Alternatives**

If neither `Object.assign()` nor the spread operator are suitable for your needs, consider using other methods to merge objects, such as:

1. **Lodash's `_merge()`**: A more robust and feature-rich method for merging objects.
2. **Ramda's `merge()`**: Another popular library for functional programming in JavaScript.

These alternatives may offer better performance or additional features depending on your specific use case.

Related benchmarks:

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

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

Created: 8 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 llama3.1:latest, generated one year ago):