Benchmark: slice vs pop to reduce last element

Script Preparation code:

var rows = (new Array(1000)).fill(null).map((val,index) => {
	return {id: `AA${index}`}
})

Tests:

slice
const lastId = rows[rows.length - 1].id; for (let i = rows.length - 1; i > -1; i--) { if (rows[i].id !== lastId) { rows.slice(0, i + 1); break; } }
pop
rows.pop()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
pop

Fastest: N/A

Slowest: N/A

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

The provided JSON represents a JavaScript microbenchmark test case created on MeasureThat.net. The test is comparing two approaches to remove the last element from an array in reverse order: using `slice()` and using `pop()` methods.

**Benchmark Definition**

The first part of the JSON defines the benchmark itself:
```json
{
    "Name": "slice vs pop to reduce last element",
    "Description": null,
    "Script Preparation Code": "var rows = (new Array(1000)).fill(null).map((val,index) => {\r\n\treturn {id: `AA${index}`}\r\n})"
}
```
Here, we have a simple array `rows` created with 1000 elements. Each element is an object with an `id` property.

**Individual Test Cases**

The second part of the JSON defines two test cases:
```json
[
    {
        "Benchmark Definition": "const lastId = rows[rows.length - 1].id;\r\nfor (let i = rows.length - 1; i > -1; i--) {\r\n  if (rows[i].id !== lastId) {\r\n    rows.slice(0, i + 1);\r\n    break;\r\n  }\r\n}",
        "Test Name": "slice"
    },
    {
        "Benchmark Definition": "rows.pop()",
        "Test Name": "pop"
    }
]
```
Each test case defines a different approach to remove the last element from the `rows` array in reverse order:

1. **Slice**: The first test case uses the `slice()` method to create a new array from the beginning of the original array up to the current index `i`. This is done to avoid mutating the original array.
2. **Pop**: The second test case simply removes the last element from the array using the `pop()` method.

**Libraries and Special Features**

There are no libraries used in this benchmark. However, there is a special feature: the use of arrow functions (e.g., `(val,index) => {\r\n\treturn {id: `AA${index}`}\r\n}`). This is a modern JavaScript syntax introduced in ECMAScript 2015.

**Options Compared**

The two test cases compare the performance of:

1. **Slice**: Using the `slice()` method to remove elements from the beginning of the array up to the current index.
2. **Pop**: Removing the last element directly using the `pop()` method.

**Pros and Cons**

Here are some pros and cons for each approach:

* **Slice**:
	+ Pros: Avoids mutating the original array, which can lead to unexpected behavior in other parts of the code.
	+ Cons: May create a new array object with more memory overhead than needed.
* **Pop**:
	+ Pros: Efficient and simple to implement, as it only modifies the array.
	+ Cons: Modifies the original array, which may cause issues if other parts of the code rely on its integrity.

**Other Considerations**

When considering these two approaches, keep in mind that:

* If you're working with large arrays or need to optimize performance, using `pop()` might be a better choice.
* However, if you want to avoid mutating the original array or ensure the integrity of the data, using `slice()` might be a better option.

As for alternatives, some other approaches could include:

* Using `filter()` method to create a new array with only the desired elements
* Using `forEach()` method to iterate over the array and remove elements one by one
* Using a custom loop or recursive function to achieve the same result

However, these alternatives may not be as efficient or intuitive as using `slice()` or `pop()`.

Related benchmarks:

slice vs pop to reduce last element (version: 0)

Comparing performance of: slice vs pop

Created: 3 years ago by: Guest

Jump to the latest result

slice

pop

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):