Benchmark: Array.prototype.slice vs spread operator proper

Script Preparation code:

var arrayX = [];
for(i=0; i< 1000; i++){
  arrayX.push(Math.random());
  arrayX.push(Math.random() + 'x');
  arrayX.push(Math.random() > 0.5);
}

Tests:

Array.prototype.slice
const copy = arrayX.slice();
spread operator
const copy = [ ...arrayX ];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.slice
spread operator

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 explanation of the benchmark.

**What is tested?**

The benchmark compares two approaches for creating a shallow copy of an array: the traditional `Array.prototype.slice()` method and the new ES6 spread operator (`[ ...arrayX ]`).

**Options compared:**

* **Traditional slice() method**: This method creates a new array by copying elements from the original array, starting from the specified index (in this case, 0) up to but not including the specified end index.
* **Spread operator (`[ ...arrayX ]`)**: This method creates a new array by spreading elements of the original array into a new array.

**Pros and cons of each approach:**

* **Traditional slice() method:**
	+ Pros:
		- Has been part of JavaScript for a long time, so it's well-supported by most browsers.
		- Can be more efficient for large arrays because it avoids creating intermediate objects.
	+ Cons:
		- Returns a shallow copy of the array, which means that nested objects within the original array will also be copied as references to the original objects. This can lead to unexpected behavior if you're not aware of this.
* **Spread operator (`[ ...arrayX ]`):**
	+ Pros:
		- Creates a deep copy of the array, meaning that nested objects are cloned instead of referenced. This is more predictable and safer than using `slice()`.
		- Is a newer feature (introduced in ES6), so it's not as widely supported by older browsers.
	+ Cons:
		- Can be slower than `slice()` because it involves creating intermediate arrays.

**Library usage:**

There is no library used in this benchmark. It's just pure JavaScript code.

**Special JS features or syntax:**

The spread operator (`[ ...arrayX ]`) is a newer feature introduced in ES6 (EcmaScript 2015). It was added to the JavaScript language to provide a concise way to create arrays from iterables.

**Other alternatives:**

If you need to create a deep copy of an array and want a more efficient alternative to the spread operator, you could consider using `Array.prototype.map()` in combination with `JSON.parse(JSON.stringify(arrayX))`. This approach is less elegant but can be faster:

```javascript
const copy = JSON.parse(JSON.stringify(arrayX));
```

This method works by serializing the original array to a string, parsing that string back into an array (which creates a deep copy of the original array), and then deserializing it from a string again.

Keep in mind that this approach can be slower than using `slice()` or the spread operator because it involves creating intermediate objects and strings. However, if you need to create a deep copy of an array for performance-critical code, this method might be worth considering.

Related benchmarks:

Array.prototype.slice vs spread operator proper (version: 0)

Compare the new ES6 spread operator with the traditional slice() method

Comparing performance of: Array.prototype.slice vs spread operator

Created: 6 years ago by: Guest

Jump to the latest result

Array.prototype.slice

spread operator

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):