Benchmark: Map vs preallocation vs push

Script Preparation code:

var array = new Array(1000000).fill(0);

Tests:

Map
const array2 = array.map((item, index) => index);
Preallocation
const array2 = new Array(1000000).fill(0); for (let i = 0; i < array2.length; i++) array2[i] = i;
Push
const array2 = [] for (let i = 0, len = 1000000; i < len; i++) array2.push(i);
no fill
const array2 = new Array(1000000) for (let i = 0; i < array2.length; i++) array2[i] = i;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map
Preallocation
Push
no fill

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared options, pros and cons of those approaches, and other considerations.

**Benchmark Overview**

The benchmark compares four different methods to create an array in JavaScript:

1. **Map**: Using the `Array.prototype.map()` method to create a new array from an existing one.
2. **Preallocation**: Creating an array with a specific length using `new Array(length)`, and then filling it with values.
3. **Push**: Using the `push()` method to add elements to an empty array.
4. **No fill** (preallocation without initialization): Creating an array with a specific length using `new Array(length)`.

**Library Usage**

In this benchmark, the `Array.prototype.map()` method is used. The `map()` method applies a provided function to each element in an array and returns a new array with the results. In this case, the function maps the index of each element to itself.

**Special JS Feature/Syntax**

The benchmark uses a modern JavaScript feature: arrow functions (introduced in ECMAScript 2015). An arrow function is a concise way to define small anonymous functions. The `map()` method's callback function is defined using an arrow function, which simplifies the code and makes it more readable.

**Comparison Options**

Here's a summary of each option:

* **Map**: Creates a new array by applying a transformation function to each element in an existing array.
	+ Pros: efficient for small arrays, easy to use, and concise syntax. Cons: creates a new array object, which can be inefficient for large arrays.
* **Preallocation**: Creates an array with a specific length using `new Array(length)`, and then fills it with values.
	+ Pros: allows for better control over the size of the array, reduces memory allocation overhead, and is more efficient than map() for large arrays. Cons: requires manual initialization of the array, which can be error-prone if not done correctly.
* **Push**: Uses the `push()` method to add elements to an empty array.
	+ Pros: allows for easy addition of multiple elements to the array, does not require manual initialization. Cons: less efficient than preallocation for large arrays, as it involves multiple array resizing operations.

**Benchmark Results**

The benchmark results show the execution per second (ExecutionsPerSecond) values for each test case:

* **Map**: 50.527732849121094
* **Preallocation**: 40.71397018432617
* **Push**: 40.71397018432617
* **No fill** (preallocation without initialization): 137.89625549316406

The results suggest that preallocation is the most efficient method for large arrays, while map() and push() are less efficient due to their overhead.

**Other Considerations**

When choosing an array creation method, consider the following factors:

* **Array size**: For small arrays, map() or push() might be sufficient. For larger arrays, preallocation might be more efficient.
* **Memory allocation**: Preallocation reduces memory allocation overhead by creating a fixed-size array upfront.
* **Code readability**: Map() and arrow functions can make code more concise and readable.

In conclusion, the benchmark highlights the importance of considering array creation methods based on the size of the data and performance requirements. While map() and push() are convenient options for small arrays, preallocation is generally a better choice for larger datasets due to its efficiency and control over memory allocation.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36

Browser/OS: Chrome 103 on Windows

View result in a separate tab

Test name	Executions per second
Map	50.5 Ops/sec
Preallocation	137.9 Ops/sec
Push	40.7 Ops/sec
no fill	183.3 Ops/sec

Related benchmarks:

Map vs preallocation vs push (version: 0)

Comparing performance of: Map vs Preallocation vs Push vs no fill

Created: 2 years ago by: Guest

Jump to the latest result

Map

Preallocation

Push

no fill

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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