Benchmark: spilce vs slice - MeasureThat.net

Script Preparation code:

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

Tests:

1
list.push(...Array(11)) list = list.slice(-11);
2
list.push(...Array(11)) list = list.splice(-11);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

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Test case name	Result
1
2

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its different approaches.

**Overview of the Benchmark**

The benchmark is designed to compare two approaches for removing the last 11 elements from an array in JavaScript: `slice()` and `splice()`. The test creates a large array with 1 million elements, pushes 11 more elements into it, and then measures which approach is faster.

**Approach 1: Using Array.prototype.slice()**

The first benchmark definition uses `Array.prototype.slice()` to remove the last 11 elements from the array:
```javascript
list.push(...Array(11))
list = list.slice(-11)
```
This approach creates a new array slice containing the last 11 elements, and then assigns it back to the original array. The pros of this approach are:

* It is more explicit and readable, as it clearly conveys the intent of removing the last elements.
* It avoids modifying the original array in place.

However, the cons are:

* It creates a new array, which can be memory-intensive for large arrays.
* It may not be the most efficient approach if the array is very large.

**Approach 2: Using Array.prototype.splice()**

The second benchmark definition uses `Array.prototype.splice()` to remove the last 11 elements from the array:
```javascript
list.push(...Array(11))
list = list.splice(-11)
```
This approach modifies the original array in place, removing the last 11 elements. The pros of this approach are:

* It is more efficient than creating a new array, as it only modifies the existing data.
* It can be faster for large arrays, since it avoids the overhead of creating a new array.

However, the cons are:

* It modifies the original array in place, which may not be desirable if the array needs to remain unchanged.
* The behavior of `splice()` can be less predictable than `slice()`, as it modifies the array and returns an array slice.

**Library Used: None**

There is no library used in this benchmark. Both approaches are built-in methods of the JavaScript Array prototype.

**Special JS Feature/ Syntax: None**

This benchmark does not use any special JavaScript features or syntax, such as async/await or decorators.

**Other Alternatives**

If you want to remove the last N elements from an array without using `slice()` or `splice()`, there are other alternatives:

* Using `Array.prototype.reduce()`: You can use `reduce()` to build a new array with the desired length, like this: `list = list.reduce((acc, curr) => acc.length < 11 ? [...acc, curr] : acc.slice(0, -11), [])`.
* Using `Array.prototype.filter()`: You can use `filter()` to create a new array with only the elements you want, like this: `list = list.filter((_, i) => i >= 11)`.
* Using a custom implementation: You can write your own function to remove the last N elements from an array.

Keep in mind that these alternatives may have different performance characteristics than `slice()` and `splice()`.

Related benchmarks:

spilce vs slice (version: 0)

Comparing performance of: 1 vs 2

Created: 2 years ago by: Guest

Jump to the latest result

1

2

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):