Benchmark: splice VS shift: who is the fastest to keep constant size

Script Preparation code:

var list = [];
for (var i = 0; i < 1000 * 1000; i++) {
  list.push(i);
}

Tests:

splice
const rv = list.splice(0, 1); console.log(rv)
shift
const rv = list.shift(); console.log(rv)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
splice
shift

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested.

**Benchmark Description**

The benchmark is comparing two ways to remove an element from the end of an array in JavaScript: `splice` and `shift`. The goal is to determine which method is faster, assuming the size of the array remains constant.

**Options Compared**

There are three options compared:

1. **Slice Loose**: This involves using the `slice()` function with no arguments to remove an element from the beginning of the array (not applicable in this case).
2. **Splice (with length 0)**: This involves using `splice(0, 0)` to remove an element from the end of the array.
3. **Shift**: This involves using `shift()` to remove and return the last element from the array.

**Pros and Cons**

Here's a brief summary:

* **Slice Loose**: Not applicable in this case since we're removing from the end, not the beginning. However, if used correctly with `slice()` and negative arguments, it can create a new array copy.
* **Splice (with length 0)**: While this method modifies the original array by removing an element at index 0 without shifting all elements to the left, its performance is generally slower than `shift` because of the overhead of updating indices.
* **Shift**: This method is efficient because it only updates the last element's position and doesn't require creating a new array or modifying other indices.

**Library**

There is no external library used in this benchmark. The tests rely solely on built-in JavaScript methods.

**Special JS Feature or Syntax**

None mentioned, but we should note that `splice()` can be used with positive arguments to remove elements from the beginning of the array, and negative arguments to remove elements from the end. In contrast, `shift()` only removes elements from the end (i.e., the last element).

**Other Considerations**

When measuring performance in JavaScript, it's essential to consider:

* **Array size**: The benchmark starts with a list of 1000 elements, which is small enough for a microbenchmark.
* **Memory allocation**: Since we're pushing and shifting elements onto the array, memory allocation might be affected. However, this should not significantly impact the results in this specific case.
* **Browser variations**: The benchmark uses Chrome 110 as the test browser, which might have different performance characteristics compared to other browsers.

**Alternatives**

If you'd like to explore alternative methods or libraries for modifying arrays, consider:

* Using `Array.prototype.reduce()` or `Array.prototype.filter()` instead of `splice` and `shift`.
* Implementing a custom array manipulation function using bitwise operations.
* Utilizing modern JavaScript features like `at()` or `forEach()` for iteration.

Keep in mind that the performance of these alternatives might vary depending on the specific use case and browser.

Related benchmarks:

splice VS shift: who is the fastest to keep constant size (version: 0)

100k list splice and shift win, they mutate list slice loose, it creates a copy of list 7.5x slower

Comparing performance of: splice vs shift

Created: 4 years ago by: Guest

Jump to the latest result

splice

shift

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):