Benchmark: map vs slice+for

Script Preparation code:

var arr1 = [];
var arr2;
for (let i = 0; i < 1000000; i++) {
  arr1[i] = i;
}

Tests:

map
arr2 = arr1.map(value => value * 2);
slice+for
arr2 = arr1.slice(); for (let i = 0, l = arr2.length; i < l; i++) { arr2[i] = arr2[i] * 2; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
map
slice+for

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 provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark is designed to compare the performance of two approaches for doubling an array of numbers:

1. `Array.prototype.map()`
2. Creating a new array using `Array.prototype.slice()` and then iterating over it using a `for` loop

**What's Being Tested?**

In this specific case, both approaches are being tested on a large array of 1 million elements.

The test is primarily concerned with comparing the execution time of these two approaches:

* `map()`: This method creates a new array with the results of applying a provided function to every element in the original array. In this case, the function doubles each value.
* `slice()` + `for` loop: This approach creates a copy of the original array using `slice()`, and then iterates over it using a `for` loop, doubling each value.

**Pros and Cons of Each Approach**

### Array.prototype.map()

Pros:

1. **Concise**: The code is shorter and more readable.
2. **Efficient**: `map()` is optimized for performance and uses a specialized internal implementation that avoids the need for explicit looping.

Cons:

1. **Creates new array**: `map()` creates a new array with the results, which can consume additional memory.
2. **May not be as performant as other methods in some cases**: While `map()` is generally efficient, it's possible that other methods (e.g., using a `for` loop or a library like Lodash) might outperform it under specific circumstances.

### Array.prototype.slice() + for loop

Pros:

1. **No memory overhead**: Since `slice()` only creates a shallow copy of the original array, there is no additional memory allocation.
2. **Control over iteration**: Using a `for` loop allows for more control over iteration and indexing.

Cons:

1. **More verbose**: The code is longer and requires explicit looping.
2. **Less efficient than map()**: While not as bad as it sounds, the `slice()` + `for` loop approach can be slower due to the overhead of creating a new array and iterating manually.

**Library and Special Features**

There are no specific libraries or special features mentioned in this benchmark. The test is designed to focus on the two approaches themselves.

**Other Alternatives**

In addition to these two approaches, there might be other ways to double an array, such as:

1. Using a `for` loop directly on the original array: This would avoid creating a new array and iterating manually.
2. Utilizing specialized libraries or functions (e.g., Lodash's `mapValues()` method) that optimize performance for this specific use case.

However, these alternatives are not being tested in this particular benchmark, so we'll leave them aside for now.

Related benchmarks:

map vs slice+for (version: 0)

Comparing performance of: map vs slice+for

Created: 3 years ago by: Guest

Jump to the latest result

map

slice+for

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):