Benchmark: slice vs new allocation1

Script Preparation code:

var arr = [];
for (let i = 0; i < 1000000; i++) {
  arr.push(i);
}

Tests:

Slice
for (let i = 0; i < 1000; i++) { arr.slice(i * 10, 1000) }
Length - 1
for (let i = 0; i < 1000; i++) { }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Slice
Length - 1

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

The provided benchmark tests two different approaches to accessing elements in an array: using the `slice()` method and not using it (i.e., accessing elements directly). This is a simple yet revealing test that can help identify performance differences between these two methods.

**Options Compared**

Two options are being compared:

1. **`arr.slice(i * 10, 1000)`**: This method creates a new array with the specified range of elements from `arr`. It's like extracting a slice from the original array.
2. **Direct Access**: Instead of using `slice()`, this option accesses elements directly by their index (`arr[i * 10]` to `arr[999]`). This approach avoids creating a new array but might be slower due to potential overflows or bounds checking.

**Pros and Cons**

* **`slice()` Method:**
	+ Pros:
		- More flexible, as you can specify a start index, end index, and step size.
		- Creates a new array with the desired elements, which can help avoid modifying the original array.
	+ Cons:
		- Can be slower due to the overhead of creating a new array.
* **Direct Access:**
	+ Pros:
		- Often faster since it avoids the overhead of creating a new array.
	+ Cons:
		- Less flexible, as you need to specify both start and end indices.
		- May cause overflows or bounds checking issues if not handled carefully.

**Library Usage**

None of the test cases explicitly use any libraries. However, MeasureThat.net may be using some internal library or framework to handle benchmarking tasks.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark. The focus is on the basic `slice()` method and direct array access.

**Other Alternatives**

If you're interested in exploring alternative approaches, here are a few:

1. **`Array.prototype.map()`**: Instead of using `slice()`, you could use `map()` to create a new array with the desired elements.
2. **`for...of` Loop**: You could use a `for...of` loop to iterate over the array and access elements directly, similar to direct access but with more concise syntax.

Example:
```javascript
for (const element of arr.slice(i * 10, 1000)) {
  // do something with each element
}
```
Keep in mind that these alternatives might have different performance characteristics depending on the specific use case and browser.

I hope this explanation helps you understand the benchmark and its design!

Related benchmarks:

slice vs new allocation1 (version: 0)

Comparing performance of: Slice vs Length - 1

Created: 3 years ago by: Guest

Jump to the latest result

Slice

Length - 1

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):