Benchmark: array item replacement performance comparisons

Script Preparation code:


var arr = Array.from({ length: 5000 }, (item, index) => index);

Tests:

Slice and splice
const changeIndex = 111; const newTestArray = arr.slice(); newTestArray.splice(changeIndex, 1, 8080);
Slice and concat
const changeIndex = 222; const newTestArray = arr.slice(0, changeIndex).concat(13, arr.slice(changeIndex + 1));
Slice and spread
const changeIndex = 333; const newTestArray = [ ...arr.slice(0, changeIndex), 42, ...arr.slice(changeIndex + 1)];
Spread and splice
const changeIndex = 444; const newTestArray = [...arr]; newTestArray.splice(changeIndex, 1, 1111);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Slice and splice
Slice and concat
Slice and spread
Spread and splice

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:89.0) Gecko/20100101 Firefox/89.0

Browser/OS: Firefox 89 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Slice and splice	30787.9 Ops/sec
Slice and concat	9678.1 Ops/sec
Slice and spread	9231.9 Ops/sec
Spread and splice	11553.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months 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 test that compares the performance of different approaches to replace an item in an array. The test is designed to measure the execution time and number of executions per second for each approach.

**Test Cases**

There are four individual test cases:

1. **Slice and Splice**: This test case uses the `splice()` method to remove an element at a specified index and then inserts a new element.
2. **Slice and Concat**: This test case uses the `slice()` method to create two slices of the array, concatenates them, and then splices the original array with the concatenated slice.
3. **Slice and Spread**: This test case uses the spread operator (`...`) to create a new array that includes all elements from the first slice, followed by a single element, and finally all elements from the second slice.
4. **Spread and Splice**: This test case uses the spread operator (`...`) to create a shallow copy of the original array and then splices it with a new element.

**Library Used**

None of the test cases explicitly use any external libraries. However, some JavaScript features, such as `const` declarations and template literals, are used throughout the benchmark code.

**Special JS Features/Syntax**

* **Template Literals**: The `var arr = Array.from({ length: 5000 }, (item, index) => index);` line uses a template literal to create an array with 5000 elements.
* **Spread Operator**: The `const newTestArray = [ ...arr.slice(0, changeIndex), 42, ...arr.slice(changeIndex + 1)];` and `const newTestArray = [...arr];` lines use the spread operator to create new arrays.

**Approach Comparison**

Here's a brief overview of each approach:

1. **Slice and Splice**: This approach is straightforward but may have overhead due to the creation of multiple slices.
2. **Slice and Concat**: This approach creates two slices, concatenates them, and then splices the original array with the concatenated slice. It might be slower than the first approach due to the additional concatenation step.
3. **Slice and Spread**: Using the spread operator can be faster than `splice()` because it avoids creating a new array and only modifies the existing one. However, it may also have some overhead due to the creation of a new array with the inserted element.
4. **Spread and Splice**: This approach uses the spread operator to create a shallow copy of the original array and then splices it with a new element. It's similar to the first approach but uses a more modern syntax.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **Slice and Splice**:
	* Pros: Simple, widely supported.
	* Cons: May have overhead due to multiple slices.
2. **Slice and Concat**:
	* Pros: Well-established pattern, easy to understand.
	* Cons: Additional concatenation step can slow it down.
3. **Slice and Spread**:
	* Pros: Can be faster than `splice()`, more modern syntax.
	* Cons: May have overhead due to spread operator creation.
4. **Spread and Splice**:
	* Pros: Similar performance to `slice()` and splice, modern syntax.
	* Cons: May have some overhead due to shallow copy.

**Other Alternatives**

Some alternative approaches could be:

1. Using a more advanced data structure, such as a linked list or a tree, to replace elements.
2. Utilizing a library like Lodash, which provides optimized array methods.
3. Implementing a custom, in-place replacement algorithm using bitwise operations or bit manipulation.

Keep in mind that these alternative approaches may have different trade-offs and overhead compared to the original test cases.

I hope this explanation helps you understand the provided benchmark!

Related benchmarks:

array item replacement performance comparisons (version: 0)

Comparing performance of: Slice and splice vs Slice and concat vs Slice and spread vs Spread and splice

Created: 3 years ago by: Guest

Jump to the latest result

Slice and splice

Slice and concat

Slice and spread

Spread and splice

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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