Benchmark: Slice vs For - 100 item

Script Preparation code:

var data = [
    1, 2, 3, 4, 5, 6, 7, 8, 9, 0,
    10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
    20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
    30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
    40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
    50, 51, 52, 53, 54, 55, 56, 57, 58, 59,
    60, 61, 62, 63, 64, 65, 66, 67, 68, 69,
    70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
    80, 81, 82, 83, 84, 85, 86, 87, 88, 89,
    90, 91, 92, 93, 94, 95, 96, 97, 98, 99
];

Tests:

slice
var copy = data.slice(0, 4);
push
var copy = []; for (var i = 0; i < 4; i++) { copy.push(data[i]) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
push

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:141.0) Gecko/20100101 Firefox/141.0

Browser/OS: Firefox 141 on Windows

View result in a separate tab

Test name	Executions per second
slice	70302896.0 Ops/sec
push	112141536.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what is being tested.

**Benchmark Definition**

The benchmark is comparing two approaches to create a copy of a subset of an array: `slice()` and `for` loop with `push()`. The benchmark definition script for each approach is included in the JSON data. Let's analyze these scripts:

1. `slice()`:
```javascript
var copy = data.slice(0, 4);
```
This script uses the `Array.prototype.slice()` method to create a shallow copy of the first 4 elements of the `data` array.

2. `push()`:
```javascript
var copy = [];
for (var i = 0; i < 4; i++) {
  copy.push(data[i]);
}
```
This script creates an empty array `copy` and then uses a `for` loop to iterate over the first 4 elements of the `data` array, pushing each element onto the `copy` array.

**Options Compared**

The benchmark is comparing two options:

1. **Slice**: Using the `Array.prototype.slice()` method to create a copy of the subset.
2. **Push**: Creating an empty array and using a `for` loop to push elements onto it.

**Pros and Cons**

Here are some pros and cons of each approach:

1. **Slice**:
	* Pros:
		+ More concise and efficient
		+ Creates a shallow copy, which can be beneficial for large datasets
	* Cons:
		+ May not work correctly with certain types of data (e.g., objects)
2. **Push**:
	* Pros:
		+ Works correctly with all types of data
		+ Allows for more control over the creation of the copy
	* Cons:
		+ Less efficient than `slice()`
		+ More verbose and error-prone

**Library and Special JS Features**

There is no specific library used in these benchmark scripts. However, it's worth noting that the `Array.prototype.slice()` method uses a V8 internal function to create the copy, which may have some performance benefits.

**Other Considerations**

When creating a copy of an array using one of these approaches, you should be aware of the following considerations:

* **Shallow vs. Deep Copy**: The `slice()` method creates a shallow copy, while a custom implementation using `push()` would create a deep copy.
* **Performance**: While the `slice()` method may be faster for large datasets, the performance difference is likely to be negligible unless you're dealing with very large arrays.

**Alternatives**

If you need to create a copy of an array in JavaScript, there are other options:

1. **Spread operator (`...`)**: Introduced in ES6, this operator creates a shallow copy of an array.
```javascript
var copy = [...data.slice(0, 4)];
```
2. **`Array.prototype.map()` method**: This method can be used to create a new array with the first `n` elements of the original array.
```javascript
var copy = data.slice(0, 4).map((x) => x);
```

These alternatives may offer better performance or more control over the creation of the copy, depending on your specific use case.

Related benchmarks:

Slice vs For - 100 item (version: 0)

Comparing performance of: slice vs push

Created: 2 years ago by: Guest

Jump to the latest result

slice

push

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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