Benchmark: Native slice vs copy

Script Preparation code:

function copy (a) {
  const l = a.length
  const b = new Array(l)
  for (let i = 0; i < l; ++i) {
    b[i] = a[i]
  }
  return b
}

function copyNative (a) {
  return a.slice(0)
}

Tests:

Native
var arr = Array(20).fill('hello') var res = copyNative(arr)
For Loop
var arr = Array(20).fill('hello') var res = copy(arr)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Native
For Loop

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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I'll break down the provided JSON and explain what's being tested in each benchmark.

**Benchmark Definition: Native slice vs copy**

This benchmark compares two approaches to create a new array that contains only a portion of the elements from an original array.

1. **Native slice**: The `copyNative` function uses the built-in `Array#slice` method to create a new array that contains only the first element of the original array.
2. **For Loop with Array preallocation**: The `copy` function creates a new array by preallocating an array with the same length as the original array, and then loops through each element, copying it from the original array to the new array.

**Options Compared**

The two approaches being compared are:

* Using the built-in `Array#slice` method (native slice)
* Creating a new array by preallocating it with the same length as the original array and then looping through each element (for loop)

**Pros and Cons of Each Approach**

1. **Native Slice:**
	* Pros:
		+ Faster, since it uses a built-in optimized function
		+ Less code to write
	* Cons:
		+ May not be as flexible or customizable as the for loop approach
2. **For Loop with Array Preallocation:**
	* Pros:
		+ More control over the resulting array's structure and content
		+ Can be more flexible if additional operations are needed on the new array
	* Cons:
		+ Generally slower, since it involves looping through each element
		+ More code to write

**Library/Feature**

The `Array#slice` method is a built-in JavaScript function that creates a shallow copy of an array segment. It's implemented in the browser's JavaScript engine and optimized for performance.

**Special JS Feature/Syntax**

There are no specific JavaScript features or syntaxes being tested in this benchmark.

**Other Considerations**

When choosing between these approaches, consider the trade-off between speed and flexibility. If you need a simple, fast solution that doesn't require extensive customization, native slice might be the better choice. However, if you need more control over the resulting array's structure or content, the for loop approach with array preallocation might be a better fit.

**Alternatives**

Other alternatives to consider when creating a new array from an existing one include:

* Using `Array.prototype.map()` or `Array.prototype.filter()`, which can create new arrays but may have different performance characteristics
* Utilizing Web Workers or other parallel computing techniques for large-scale data processing
* Leveraging specialized libraries or frameworks, such as Redux or MobX, that provide optimized array manipulation functions.

Related benchmarks:

Native slice vs copy (version: 0)

Array#slice vs for loop with array preallocation

Comparing performance of: Native vs For Loop

Created: 8 years ago by: Guest

Jump to the latest result

Native

For Loop

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):