Benchmark: Getting/Keeping only the first item of an array: length VS splice VS slice

Getting/Keeping only the first item of an array: length VS splice VS slice (version: 0)

Based on https://stackoverflow.com/questions/39510821/how-to-remove-all-element-from-array-except-the-first-one-in-javascript. All results should output "a" in the console using console.log(arr).

Comparing performance of: length vs splice vs slice

Created: 2 years ago by: Registered User

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Script Preparation code:

var arr = ['a','b','c','d','e','f'];

Tests:

length
arr.length = 1;
splice
arr.splice(1);
slice
arr.slice(0, 1)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
length
splice
slice

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

Browser/OS: Chrome 122 on Windows

View result in a separate tab

Test name	Executions per second
length	12330808.0 Ops/sec
splice	15247129.0 Ops/sec
slice	15140800.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview**

The provided benchmark measures the performance of three different approaches to retrieve only the first item from an array in JavaScript: using `Array.length`, `Array.splice()`, and `Array.slice()`. The goal is to determine which approach is the most efficient.

**Test Case 1: `length`**

This test case checks how long it takes to access the length property of an array with a single element. The idea behind this test is to measure the overhead of accessing the array's properties and determine if there's any difference in performance between using `arr.length` or simply checking if the array is not empty.

**Test Case 2: `splice()`**

This test case measures how long it takes to remove all elements from an array except for the first one using the `splice()` method. This approach modifies the original array, which may have performance implications.

Pros:

* Simple and intuitive way to remove all but the first element.
* Works even if the array is empty.

Cons:

* Modifies the original array, which can be inefficient if the array needs to remain unchanged.
* Can lead to unexpected behavior or side effects if used incorrectly.

**Test Case 3: `slice()`**

This test case measures how long it takes to retrieve only the first element from an array using the `slice()` method. This approach returns a new array with the desired elements without modifying the original array.

Pros:

* Returns a new array, preserving the original data.
* Does not modify the original array.

Cons:

* Creates a new array object, which can be memory-intensive for large arrays.
* May have overhead due to creating and managing additional objects.

**Library**

None of the test cases rely on any external libraries. The tests are designed to demonstrate basic JavaScript functionality.

**Special JS Feature/Syntax**

None of the provided test cases use special JavaScript features or syntax beyond standard ECMAScript 2022 features. They focus on demonstrating fundamental array manipulation techniques.

**Other Alternatives**

Some alternative approaches to achieve similar results include:

* Using `Array.prototype.reduce()`: This method can be used to remove all but the first element from an array by reducing it with a callback function that returns the first element when the accumulator reaches zero.
* Utilizing `Array.prototype.map()` and `Array.prototype.slice()`: You could use `map()` to create a new array with only the first element and then use `slice()` to get the desired result. However, this approach would be less efficient than using `slice()` alone.

**Benchmark Considerations**

When interpreting benchmark results, consider the following factors:

* Device platform and operating system: The provided benchmark data is from a Windows Desktop device.
* Browser version: The test was run in Chrome 122.
* Number of executions per second: The higher execution rate indicates better performance.

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