Benchmark: JavaScript spread operator vs Slice/Splice performance 2edas

Script Preparation code:

const ITERATIONS = 500000;
var index = ITERATIONS/2;
var n = Math.random();

var list = [];
for (let i = 0; i < length; i += 1) {
  list.push(Math.random());
}

Tests:

Array clone with spread operator
const clone = [...list];
Array clone with slice
const clone = list.slice();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array clone with spread operator
Array clone with slice

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 benchmark and analyze what's being tested.

**Benchmark Overview**

The benchmark measures the performance of two ways to create a shallow copy of an array in JavaScript: using the spread operator (`...`) and using the `slice()` method. The test is designed to identify which approach is faster, more efficient, and scalable.

**Test Case 1: Array clone with spread operator**

In this test case, the benchmark creates an array `list` with a random length (between 0 and the total number of iterations) and then uses the spread operator (`...`) to create a shallow copy of the array. The code is as follows:
```javascript
const clone = [...list];
```
**Test Case 2: Array clone with slice**

In this test case, the benchmark creates an array `list` with a random length (between 0 and the total number of iterations) and then uses the `slice()` method to create a shallow copy of the array. The code is as follows:
```javascript
const clone = list.slice();
```
**Options Compared**

The two test cases compare the performance of:

1. **Spread Operator (`...`)**: creates a new array by spreading the original array's elements.
2. **Slice Method (`slice()`)**: returns a shallow copy of a portion of an array, starting at the specified index.

**Pros and Cons of Each Approach**

* **Spread Operator (`...`)**
	+ Pros:
		- Creates a new array without modifying the original array.
		- Can be used to create arrays with more than two dimensions (e.g., `[...array, [innerArray]]`).
		- Can be used to concatenate arrays.
	+ Cons:
		- May incur higher memory overhead due to creating a new array object.
		- Can lead to performance issues if the original array is very large or complex.
* **Slice Method (`slice()`)**
	+ Pros:
		- Fast and efficient, especially for smaller arrays.
		- Returns a reference to the original array's elements in memory.
		- Does not create a new array object, which can reduce memory overhead.
	+ Cons:
		- Modifies the original array by creating a temporary copy of the slice.

**Library Used**

In this benchmark, no libraries are explicitly mentioned. However, it is worth noting that the `slice()` method is part of the JavaScript standard library and has been available since ECMAScript 5 (2011).

**Special JS Feature or Syntax**

There is no specific JavaScript feature or syntax being tested in this benchmark, as both test cases only use standard JavaScript constructs.

**Other Considerations**

When working with arrays, it's essential to consider factors such as:

* Memory allocation and deallocation
* Cache performance
* Garbage collection overhead

The spread operator and slice method can have different effects on these factors, depending on the specific use case and performance requirements.

**Alternatives**

If you need to create a shallow copy of an array in JavaScript, other alternatives include:

1. `Array.prototype.slice.call(array)`: creates a new array from the elements of another array.
2. `Array.prototype.reduce()`: can be used to create a new array by applying a reducer function to each element of the original array.
3. Libraries like Lodash's `cloneDeep()` or Immutable.js, which provide more advanced data structure manipulation capabilities.

In conclusion, this benchmark measures the performance of two ways to create a shallow copy of an array in JavaScript: using the spread operator and the slice method. Understanding the pros and cons of each approach can help you choose the most efficient solution for your specific use case.

Related benchmarks:

JavaScript spread operator vs Slice/Splice performance 2edas (version: 0)

Comparing performance of: Array clone with spread operator vs Array clone with slice

Created: 4 years ago by: Guest

Jump to the latest result

Array clone with spread operator

Array clone with slice

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):