Benchmark: Array slice vs spread

HTML Preparation code:


<script src=''></script>

Script Preparation code:

var arr = []
for (let i = 0; i < 1000; i++) {
  arr.push(i)
}

Tests:

.slice()
const n = arr.slice()
spread
const n = [...arr]

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:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.67 Safari/537.36

Browser/OS: Chrome 87 on Windows

View result in a separate tab

Test name	Executions per second
.slice()	1437480.9 Ops/sec
spread	1423314.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark is designed to compare two approaches for creating a shallow copy of an array: using the `.slice()` method versus the spread operator (`[...spread]`).

**Options Compared**

Two options are being compared:

1. **`.slice()`:** This method returns a new array containing the elements from the original array, starting at the specified index (in this case, 0) and ending at the end of the array.
2. **Spread operator (`[...spread]`):** This creates a new array by spreading the elements of the original array into a new array.

**Pros and Cons**

* `.slice()`:
	+ Pros: Efficient for large arrays (as it only copies references to the original elements), easy to use, and widely supported.
	+ Cons: Can be slower than the spread operator for small arrays, and its performance can degrade if the original array is modified while iterating over the slice.
* Spread operator (`[...spread]`):
	+ Pros: Creates a new copy of the entire array, which can be beneficial when working with large datasets or when you need to ensure that modifications to the original array do not affect the copied array. It's also more intuitive and easier to read for some developers.
	+ Cons: Can be slower than `.slice()` for very large arrays (as it creates a new copy of each element), and its performance can degrade if the spread operator is used in combination with other operations that modify the original array.

**Library and Special JS Feature**

The benchmark does not use any external libraries, but it does utilize some special JavaScript features:

* The `for...of` loop (used in the `Script Preparation Code`) is a modern iteration syntax introduced in ECMAScript 2015 (ES6). It allows for more concise and expressive code.
* The spread operator (`[...spread]`) is also a feature introduced in ES6.

**Other Considerations**

When choosing between these two approaches, consider the following:

* If you need to create a shallow copy of an array for performance-critical code, `.slice()` might be a better choice due to its efficiency.
* If you need to ensure that modifications to the original array do not affect the copied array, or if you prefer a more intuitive and readable syntax, the spread operator might be a better fit.

**Other Alternatives**

Alternative approaches for creating a shallow copy of an array include:

* Using `Array.prototype.concat()` and then assigning the result back to the variable.
* Using `Array.from()` with an iterator function that returns the elements of the original array.
* Using a library like Lodash, which provides a `cloneDeep()` function for deep copying arrays.

Keep in mind that these alternatives may have different trade-offs in terms of performance, readability, and maintainability compared to `.slice()` and the spread operator.

Related benchmarks:

Array slice vs spread (version: 0)

`.slice()` vs `[...spread]`

Comparing performance of: .slice() vs spread

Created: 4 years ago by: Guest

Jump to the latest result

.slice()

spread

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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