Benchmark: JavaScript spread operator vs Object.assign performance with empty target

Tests:

Using the spread operator
const startingValue = { sample1: 'Hello World', sample2: [1,2,3,4], sample3: undefined } const finalObject = { ...startingValue, sample3: [1,2,3,4,5,6,7,8,9] };
Using Object.assign
const startingValue = { sample1: 'Hello World', sample2: [1,2,3,4], sample3: undefined } const finalObject = Object.assign({}, startingValue, {sample3: [1,2,3,4,5,6,7,8,9]} );

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

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared, and other considerations.

**Benchmark Definition**

The benchmark tests two approaches for merging objects in JavaScript:

1. Using the spread operator (`...`)
2. Using `Object.assign()`

The benchmark defines a starting object with three properties: `sample1`, `sample2`, and `sample3`. The values of these properties are set to different types (string, array, and undefined).

**Benchmark Preparation Code**

Since there is no script preparation code provided, we'll have to infer the setup based on the benchmark definitions. It's likely that both approaches use a similar setup:

```javascript
const startingValue = { sample1: 'Hello World', sample2: [1,2,3,4], sample3: undefined };
```

**Individual Test Cases**

There are two test cases, each with its own Benchmark Definition.

1. **Using the spread operator**

```javascript
const finalObject = {
  ...startingValue,
  sample3: [1,2,3,4,5,6,7,8,9]
};
```

This approach uses the spread operator (`...`) to create a new object that includes all properties from `startingValue`, with additional property `sample3` added.

2. **Using Object.assign()**

```javascript
const finalObject = Object.assign({}, startingValue, { sample3: [1,2,3,4,5,6,7,8,9] });
```

This approach uses the `Object.assign()` method to create a new object that includes all properties from `startingValue`, with additional property `sample3` added.

**Pros and Cons**

Here are some pros and cons of each approach:

* **Using the spread operator (`...`)**
	+ Pros:
		- More concise and expressive syntax.
		- Works for objects with nested structures (e.g., arrays, objects).
	+ Cons:
		- May not work as expected in older browsers or environments without support for `...`.
		- Can be slower than `Object.assign()` due to the overhead of function calls.
* **Using Object.assign()**
	+ Pros:
		- Widely supported across modern browsers and Node.js environments.
		- Generally faster than the spread operator due to its optimized implementation.
	+ Cons:
		- Requires more code and can be less readable, especially for complex objects.

**Library/Feature Considerations**

In this benchmark, there is no explicit use of any libraries or special JavaScript features beyond the standard `Object` and `Array` types. However, it's worth noting that modern browsers often have additional features enabled by default, such as strict mode or arrow functions, which may affect the behavior of these benchmarks.

**Other Alternatives**

Alternative approaches for merging objects in JavaScript include:

* **Lodash's `merge()` function**: This is a popular utility library that provides various ways to merge objects.
* **Merging with destructuring assignment**: Another way to merge objects using destructuring assignment, which can be more concise and readable in some cases.

```javascript
const { merge } = require('lodash');

const finalObject = merge({}, startingValue, { sample3: [1,2,3,4,5,6,7,8,9] });
```

Keep in mind that these alternatives may have different performance characteristics or trade-offs in terms of readability and conciseness.

Related benchmarks:

JavaScript spread operator vs Object.assign performance with empty target (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):