Benchmark: arr.slice() vs [...arr]

Script Preparation code:


var arr = ['', '', ''];
for(i=0; i<10; i++){}

Tests:

Slice
var arr = [['1', '2', '3','4','5','a','b','c','d','e'],['1', '2', '3','4','5','a','b','c','d','e'],['1', '2', '3','4','5','a','b','c','d','e']]; var arr2=[]; for(let i=0;i<3;i++){ arr2.push(arr[i].slice()); }
Spread
var arr = [['1', '2', '3','4','5','a','b','c','d','e'],['1', '2', '3','4','5','a','b','c','d','e'],['1', '2', '3','4','5','a','b','c','d','e']]; var arr2=[]; for(let i=0;i<3;i++){ arr2.push([...arr[i]]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Slice
Spread

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 break down the provided JSON and benchmark to understand what is being tested.

**Benchmark Definition**

The benchmark tests two approaches for creating a new array from an existing one:

1. `arr.slice()`: This method creates a shallow copy of a portion of an array, which returns a new array object.
2. `[...arr]`: This syntax uses the spread operator to create a new array by copying elements from an existing array.

**Options Compared**

The benchmark compares these two approaches for creating a new array from an existing one, specifically when dealing with arrays containing arrays (i.e., multi-dimensional arrays).

**Pros and Cons**

* **`arr.slice()`**:
	+ Pros: Generally faster than the spread operator, as it uses a more efficient algorithm.
	+ Cons: Can be slower in certain cases, such as when dealing with large arrays or complex data structures. Additionally, `slice()` returns an array object, which can lead to additional memory allocations if not properly managed.
* **[...arr]**:
	+ Pros: More concise and expressive syntax compared to `slice()`. It also provides a more intuitive way of handling multi-dimensional arrays.
	+ Cons: Can be slower than `slice()` due to the overhead of creating a new array object using the spread operator. Additionally, it may not perform as well for very large datasets.

**Library Used**

None in this benchmark definition. However, some libraries like Lodash or Ramda might provide alternative functions for working with arrays and objects.

**Special JS Feature/Syntax**

The use of the spread operator (`[...arr]`) is a recent JavaScript feature introduced in ECMAScript 2015 (ES6). It allows for more concise syntax when working with arrays, tuples, or other iterable objects.

**Other Alternatives**

If you need to create a new array from an existing one, there are alternative approaches:

* Using `Array.prototype.map()` and `Array.prototype.concat()`: This approach involves mapping each element of the original array to a new value and then concatenating the resulting arrays.
* Using `Array.prototype.reduce()` and `Array.prototype.push()`: This approach involves reducing the original array to an accumulator array by pushing elements from the original array into it.

Example code for alternative approaches:
```javascript
// Using map() and concat()
var arr = [['1', '2', '3','4','5','a','b','c','d','e']];
var newArr = arr.map((item) => [...item]).concat();
```

```javascript
// Using reduce() and push()
var arr = [['1', '2', '3','4','5','a','b','c','d','e']];
var newArr = arr.reduce((acc, item) => acc.concat([...item]), []);
```
Keep in mind that these alternative approaches may have different performance characteristics compared to the original `slice()` and spread operator methods.

Related benchmarks:

arr.slice() vs [...arr] (version: 0)

Test the .slice() method versus [...] when creating a new array from another one.

Comparing performance of: Slice vs Spread

Created: 3 years ago by: Guest

Jump to the latest result

Slice

Spread

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):