Benchmark: JS Array Slice vs Array Spread

Script Preparation code:

const ITERATIONS = 500000;

var list = [];
for (let i = 0; i < ITERATIONS; 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 dive into the explanation of the provided JSON benchmark.

**Benchmark Overview**

The benchmark, named "JS Array Slice vs Array Spread," tests the performance of two approaches to create an array clone: using the spread operator (`[...]`) and using the `slice()` method.

**Script Preparation Code**

The script preparation code creates a large array `list` with 500,000 elements, each containing a random number between 0 and 1. This is done using a simple loop that pushes new elements to the array.

```javascript
const ITERATIONS = 500000;
var list = [];
for (let i = 0; i < ITERATIONS; i += 1) {
    list.push(Math.random());
}
```

**Html Preparation Code**

There is no HTML preparation code provided, which means that this benchmark does not test any specific web browser's rendering or layout-related performance.

**Test Cases**

The benchmark consists of two individual test cases:

1. **Array clone with spread operator**

```javascript
const clone = [...list];
```

This creates a new array `clone` by spreading the elements of the original array `list`.

2. **Array clone with slice**

```javascript
const clone = list.slice();
```

This uses the `slice()` method to create a new array `clone`, copying the elements from the original array `list`. The `slice()` method returns a shallow copy of the specified portion of an array.

**Performance Comparison**

The benchmark compares the performance of these two approaches:

1. **Spread Operator (Array clone with spread operator)**: This approach creates a new array by spreading the elements of the original array. It uses the rest operator (`...`) to create a new array and copies the elements from the original array into this new array.
2. **Slice Method**: This approach uses the `slice()` method to create a new array, copying the elements from the original array.

**Pros and Cons**

**Spread Operator (Array clone with spread operator)**:

Pros:

* Creates a shallow copy of the array, which is sufficient for most use cases.
* Can be more readable and concise than using the `slice()` method.

Cons:

* May not work as expected if the array contains objects or other complex data structures.
* May have performance implications due to the creation of a new array object.

**Slice Method (Array clone with slice)**:

Pros:

* Creates a shallow copy of the entire array, including all elements and their properties.
* Can be more efficient than using the spread operator for very large arrays.

Cons:

* Returns an array object that is not the same as the original array, which may have implications for certain use cases.
* May be less readable and more verbose than using the spread operator.

**Library and Special JS Features**

Neither of these approaches uses any libraries or special JavaScript features. The benchmark only tests the performance of the two array cloning methods themselves.

**Other Alternatives**

There are other ways to create an array clone, such as:

* Using the `concat()` method: `const clone = list.concat()`
* Using a library like Lodash's `cloneDeep()` function
* Using a polyfill for older browsers that may not support modern array cloning methods

However, these alternatives are not part of this benchmark and are not being tested.

Related benchmarks:

JS Array Slice vs Array Spread (version: 0)

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

Created: 3 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):