Benchmark: JavaScript spread operator vs Slice 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 = firstObject.slice().concat(secondObject.slice())

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:

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

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Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Overview**

The MeasureThat.net benchmark is designed to compare the performance of two approaches: using the spread operator (`...`) and `Object.assign()` to concatenate arrays or objects in JavaScript.

**Script Preparation Code**

Since there is no Script Preparation Code provided, we will assume that it's a simple script that creates two sample objects and uses either the spread operator or `Object.assign()` to concatenate them.

**Individual Test Cases**

There are two test cases:

1. **Using the Spread Operator**: This test case uses the spread operator (`...`) to concatenate two objects: `firstObject` and `secondObject`. The resulting object is stored in the `finalObject`.
```javascript
const firstObject = [{ sampleData: 'Hello world' }];
const secondObject = [{ moreData: 'foo bar' }];
const finalObject = [...firstObject, ...secondObject];
```
2. **Using Object.assign**: This test case uses `Object.assign()` to concatenate two arrays: `firstObject` and `secondObject`. The resulting array is stored in the `finalArray`.
```javascript
const firstObject = [{ sampleData: 'Hello world' }];
const secondObject = [{ moreData: 'foo bar' }];
const finalArray = Object.assign([], firstObject).concat(secondObject.slice());
```
**Pros and Cons**

1. **Using the Spread Operator**:
	* Pros:
		+ Shorter and more concise syntax.
		+ Better readability, especially when concatenating arrays or objects with a small number of properties.
	* Cons:
		+ Can be slower due to function call overhead (e.g., `Array.prototype.push()`).
		+ May not work as expected when dealing with complex data structures or large datasets.
2. **Using Object.assign**:
	* Pros:
		+ Can be faster for large datasets, as it avoids the function call overhead of `push()`.
		+ Works well with more complex data structures and large datasets.
	* Cons:
		+ Less readable syntax, especially when concatenating arrays or objects.
		+ May require additional setup (e.g., creating an empty array) before using.

**Libraries and Special JS Features**

In this benchmark, we don't see any specific libraries being used. However, it's worth noting that `Object.assign()` has been a part of the JavaScript standard library since ECMAScript 2015 (ES6).

There are no special JS features mentioned in the test cases.

**Other Alternatives**

If you're looking for alternative approaches to concatenate arrays or objects, here are some options:

* **Using `Array.prototype.concat()`**: This method is similar to `Object.assign()`, but it's a built-in array method that avoids the need for an additional function call.
```javascript
const finalArray = firstObject.concat(secondObject);
```
* **Using a custom concatenation function**: You can create a custom function to concatenate arrays or objects, which might be more readable and efficient than using `Object.assign()`.
```javascript
function concatArrays(arr1, arr2) {
  return [...arr1, ...arr2];
}

const finalArray = concatArrays(firstObject, secondObject);
```
* **Using the `flatMap()` method**: If you're working with arrays, you can use the `flatMap()` method to concatenate them.
```javascript
const finalArray = firstObject.flatMap((item) => secondObject.map((otherItem) => [item, otherItem]));
```

Related benchmarks:

JavaScript spread operator vs Slice performance (version: 0)

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

Created: 7 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):