Benchmark: Shift vs Slice - MeasureThat.net

Script Preparation code:

var arr = Array.from({ length: 120000 }, (_, i) => i)

Tests:

Shift
for (let i = 0; i < arr.length - 100; i++) { arr.shift(); }
Slice
arr.slice(-100)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Shift
Slice

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.

**Benchmark Overview**

The provided JSON represents a benchmark that compares the performance of two approaches: shifting elements in an array using `arr.shift()` and slicing an array to get the last 100 elements using `arr.slice(-100)`. The benchmark is designed to test these two approaches on large arrays of varying sizes.

**Options Compared**

Two options are being compared:

1. **Shift**: This approach involves repeatedly calling `arr.shift()` until a certain number of elements have been removed from the array.
2. **Slice**: This approach involves calling `arr.slice(-100)` to get the last 100 elements of the array.

**Pros and Cons of Each Approach**

Here's a brief overview of each approach:

1. **Shift**
	* Pros:
		+ Can be useful when working with large arrays where memory is limited, as it doesn't require creating a new array.
		+ Can be faster than slicing for very small arrays or arrays with many elements at the beginning that need to be processed first.
	* Cons:
		+ Can be slower than slicing due to the overhead of repeatedly removing elements from the array's head.
		+ May cause issues when working with arrays where elements are added at the end, as shifting can push elements to the front of the array.
2. **Slice**
	* Pros:
		+ More predictable and consistent performance across different browsers and environments.
		+ Easier to understand and maintain, especially for developers not familiar with the `shift()` method.
	* Cons:
		+ Creates a new array, which can be memory-intensive for very large arrays.
		+ May be slower than shifting for small arrays or arrays where elements are added at the end.

**Library and Special JS Features**

There is no library explicitly mentioned in the provided JSON. However, it's worth noting that JavaScript engines like V8 (used by Chrome) have optimizations and features that can affect benchmark results. For example, modern browsers may use `Array.prototype.slice()` to create a new array, which can impact performance.

**Test Case Special JS Feature**

There is no special JavaScript feature or syntax used in this benchmark.

**Alternatives**

Other alternatives for implementing these approaches include:

1. **Splice**: Instead of using `shift()`, you could use `arr.splice(0, 100)` to remove the first 100 elements from the array.
2. **Array.prototype.subarray()**: This method creates a new array with a specified number of elements starting at a given index. It can be used as an alternative to slicing.

Keep in mind that these alternatives may have different performance characteristics and might not be suitable for all use cases.

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

Related benchmarks:

Shift vs Slice (version: 0)

Comparing performance of: Shift vs Slice

Created: 3 years ago by: Guest

Jump to the latest result

Shift

Slice

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):