Benchmark: edit map vs slice no index start

Script Preparation code:

window.arr = new Array(2000).fill({value: 'old'});
arr[0] = {value: 'toReplace'};

Tests:

map
const newArr = arr.map((item) => item.value === 'toReplace' ? {value: 'new'} : item);
slice
const editIndex = arr.findIndex(item => item.value === 'toReplace'); const newArr = [ ...arr.slice(0, editIndex), {value: 'new'}, ...arr.slice(editIndex + 1), ];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
map
slice

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down the JavaScript microbenchmark on MeasureThat.net.

**Benchmark Definition**

The benchmark defines two test cases: `map` and `slice`. Both tests compare the performance of array manipulation methods in JavaScript. The goal is to determine which approach is faster.

**Script Preparation Code**

Before running the benchmarks, a script prepares an array `arr` with 2000 elements, each containing a string value. One element is set to `'toReplace'`, which will be used as a replacement value later on.

```javascript
window.arr = new Array(2000).fill({value: 'old'});
arr[0] = {value: 'toReplace'};
```

**Html Preparation Code**

There's no HTML preparation code, indicating that the benchmark only focuses on JavaScript performance and doesn't require any DOM-related setup.

**Test Cases**

The two test cases are:

1. `map`
2. `slice`

Let's analyze each test case:

### map

This test case uses the `map()` method to create a new array with modified elements. The callback function checks if the current element's value is equal to `'toReplace'`. If true, it returns an object with a new value; otherwise, it returns the original element.

```javascript
const newArr = arr.map((item) => item.value === 'toReplace' ? {value: 'new'} : item);
```

**Pros and Cons**

* **Pros:** `map()` is a concise and expressive way to transform arrays. It's also relatively fast, especially for large arrays.
* **Cons:** Creating a new array with the same length as the original can be memory-intensive.

### slice

This test case uses the `slice()` method to create a new array with modified elements. The code extracts the first part of the array up to the index where the element with value `'toReplace'` is found, adds a new element at that position, and then concatenates the remaining parts of the original array.

```javascript
const editIndex = arr.findIndex(item => item.value === 'toReplace');
const newArr = [
  ...arr.slice(0, editIndex),
  {value: 'new'},
  ...arr.slice(editIndex + 1)
];
```

**Pros and Cons**

* **Pros:** `slice()` is generally faster than `map()` when dealing with large arrays, as it avoids creating a new array with the same length.
* **Cons:** The code can be less readable due to the use of the `findIndex` method and string concatenation.

**Libraries and Features**

There are no notable libraries used in these test cases. However, the use of `slice()` implies that the JavaScript engine uses optimized implementations for this method.

No special JS features or syntax are used in these tests. The focus is solely on comparing the performance of array manipulation methods.

**Alternatives**

Other alternatives for array manipulation might include:

* Using `forEach` with a callback function
* Utilizing libraries like Lodash, which provides various utility functions for working with arrays
* Employing other data structures, such as linked lists or sets, depending on specific requirements

Please note that the performance difference between these methods may depend on factors like JavaScript engine optimizations, hardware, and array size. MeasureThat.net's benchmarks provide a controlled environment to compare performance under different conditions.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 13_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 13 on iOS 13.3.1

View result in a separate tab

Test name	Executions per second
map	114603.2 Ops/sec
slice	156458.7 Ops/sec

Related benchmarks:

edit map vs slice no index start (version: 0)

Which is faster?

Comparing performance of: map vs slice

Created: 4 years ago by: Guest

Jump to the latest result

map

slice

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):