Benchmark: Array.prototype.slice vs spread operator with long arrays

Script Preparation code:

var params = [];
for (var i = 0; i < 500; i++) {
  params.push(i + '_hi there'); 
  params.push(true);
  params.push(i);
}

Tests:

Array.prototype.slice
var other = params.slice();
spread operator
var other = [ ...params ]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.slice
spread operator

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 benchmark.

**What is tested?**

The provided JSON represents a JavaScript microbenchmark that compares two approaches to create a shallow copy of an array: `Array.prototype.slice()` and the new ES6 spread operator (`...`). The benchmark tests which approach is faster for long arrays.

**Options compared**

There are two options being compared:

1. **`Array.prototype.slice()`**: This method creates a shallow copy of an array by returning a new array object with references to the original elements.
2. **ES6 spread operator (`...`)**: This operator creates a new array by taking the elements from an existing array.

**Pros and Cons**

Here's a brief overview of each approach:

* `Array.prototype.slice()`: Pros:
	+ Widely supported across browsers and versions
	+ Efficient for small to medium-sized arrays
Cons:
	+ Creates a new array object with references to the original elements, which can lead to unnecessary copies for very large arrays.
* ES6 spread operator (`...`): Pros:
	+ More concise and expressive than `Array.prototype.slice()`
	+ More efficient for very large arrays because it avoids creating intermediate objects
Cons:
	+ Not as widely supported across browsers and versions (although improving)
	+ May have performance issues in older browsers

**Library and syntax**

There is no external library being used in this benchmark. The spread operator (`...`) is a built-in JavaScript feature introduced in ES6.

**Special JS features or syntax**

The benchmark uses the ES6 spread operator (`...`), which was introduced as a new syntax feature in ES6.

**Other alternatives**

While not directly related to the `Array.prototype.slice()` vs spread operator comparison, other approaches to create shallow copies of arrays include:

* `Array.from()`: Creates a new array from an iterable or array.
* `_copyArray()` or `_cloneArray()` functions: Custom functions that manually iterate through the original array and create a new copy.

Keep in mind that these alternatives may have different performance characteristics compared to the spread operator.

**Benchmark preparation code**

The provided `Script Preparation Code` initializes an empty array `params` with 500 elements, using a loop. This creates a long array for the benchmark.

**Individual test cases**

Each test case is represented by a separate object in the JSON array:

* The first test case uses `Array.prototype.slice()`: Creates a new array by calling `slice()` on the original array.
* The second test case uses the ES6 spread operator (`...`): Creates a new array by using the spread operator to take elements from the original array.

The benchmark runs both test cases and reports their performance results.

Related benchmarks:

Array.prototype.slice vs spread operator with long arrays (version: 0)

Compare the new ES6 spread operator with the traditional slice() method

Comparing performance of: Array.prototype.slice vs spread operator

Created: 6 years ago by: Guest

Jump to the latest result

Array.prototype.slice

spread operator

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):