Benchmark: copy and index vs map replace

Script Preparation code:

var test=Array.from({length: 100},()=>Math.random());

Tests:

slice
const copy = [...test]; copy[50] = 'filtered';
filter
test.map((e,i) => i!=50 ? e : 'filtered');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
filter

Fastest: N/A

Slowest: N/A

Latest run results:

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

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

**Benchmark Overview**

The benchmark is comparing two approaches to modify an array:

1. `copy` approach: Creating a shallow copy of the original array using the spread operator (`[...]`) and then modifying the copied array.
2. `map` + `replace` approach: Using the `map()` method to create a new array with modified elements, and then replacing some elements in the resulting array.

**Options Being Compared**

The benchmark is comparing these two approaches:

1. **Copy Approach**: Creating a shallow copy of the original array using `[...]`. This approach creates a new reference to the original array's elements.
2. **Map + Replace Approach**: Using `map()` to create a new array with modified elements and then replacing some elements in the resulting array.

**Pros and Cons**

**Copy Approach**

Pros:

* More intuitive for many developers, as it mirrors how you would manually modify an array.
* Can be faster if the original array is large, since no unnecessary computations are required.

Cons:

* Creates a new reference to the original array's elements, which can lead to unexpected behavior in certain scenarios (e.g., when modifying the copied array).
* May not be optimized for performance, especially for large arrays.

**Map + Replace Approach**

Pros:

* Optimized for performance, as it uses the `map()` method, which is designed for efficient array manipulation.
* Avoids creating a new reference to the original array's elements, reducing potential issues.

Cons:

* Can be less intuitive for some developers, as it requires understanding of the `map()` method and its behavior.
* May lead to unexpected behavior if not used carefully (e.g., modifying the resulting array without proper consideration).

**Library Used**

The `Array.from` method is used in the script preparation code. This method creates a new Array instance from an iterable or array-like object, such as a generator expression.

In this case, it's used to create an array with 100 random elements.

No other libraries are explicitly mentioned in the provided benchmark code.

**Special JavaScript Feature/Syntax**

There is no special JavaScript feature or syntax being tested in this benchmark. The focus is on comparing two approaches to modify an array.

**Alternatives**

For those interested, here are some alternative approaches to modifying arrays:

* Using `slice()` and assignment: `var copy = test.slice(0, 50); copy[50] = 'filtered';`
* Using `splice()`: `test.splice(50, 1, 'filtered');`
* Using a `for` loop: `for (var i = 0; i < 100; i++) { if (i == 50) { test[i] = 'filtered'; } }`

Keep in mind that these alternatives might have different performance characteristics and trade-offs compared to the `copy` and `map + replace` approaches.

Related benchmarks:

copy and index vs map replace (version: 0)

Comparing performance of: slice vs filter

Created: 2 years ago by: Guest

Jump to the latest result

slice

filter

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):