Benchmark: Create New Array & Fill it

Script Preparation code:

var length = 1000000;
var fillWith = 5;

Tests:

Map
const array = [...Array(length)].map(() => fillWith);
Array.apply + Fill
const array = Array.apply([], { length }).fill(fillWith);
While Loop
let index = length - 1; const array = []; while (index-- > 0) array[index] = fillWith;
For Loop
const array = []; for (let index = length - 1; index >= 0; index--) array[index] = fillWith;
New Array + Fill
const array = new Array(length).fill(fillWith);
Array Literal With Length + Fill
const array = []; array.length = length; array.fill(fillWith);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map
Array.apply + Fill
While Loop
For Loop
New Array + Fill
Array Literal With Length + Fill

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.83 Safari/537.36

Browser/OS: Chrome 99 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Map	21.6 Ops/sec
Array.apply + Fill	0.0 Ops/sec
While Loop	16.2 Ops/sec
For Loop	16.2 Ops/sec
New Array + Fill	856.0 Ops/sec
Array Literal With Length + Fill	847.9 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the JavaScript microbenchmark and explain what's being tested.

**Benchmark Purpose:**
The benchmark measures the performance of different ways to create and fill an array in JavaScript.

**Options Compared:**

1. `Array.prototype.map()`
2. `Array.apply()` with a custom length and fill value
3. While loop
4. For loop
5. `new Array(length).fill(fillValue)` (a modern way of creating arrays)
6. `[]` literal with `length` property set to the desired size, followed by `fill()` method

**Pros and Cons:**

1. **`Array.prototype.map()`**: Pros - concise and readable; Cons - may incur additional overhead due to iterating over the array.
2. **`Array.apply()` with a custom length and fill value**: Pros - allows for fine-grained control over the array's creation; Cons - can be less readable and may have performance implications due to the use of `apply()`.
3. **While loop**: Pros - can be more efficient in some cases since it avoids creating an intermediate array; Cons - may require additional variables and logic.
4. **For loop**: Pros - similar to while loops, but with a more traditional approach; Cons - also requires additional variables and logic.
5. **`new Array(length).fill(fillValue)`**: Pros - modern, concise, and efficient; Cons - not supported in older browsers.
6. **`[]` literal with `length` property set to the desired size, followed by `fill()` method**: Pros - concise and readable; Cons - may have performance implications due to the use of `fill()`

**Library Usage:**
None of the options directly use a JavaScript library.

**Special JS Features/Syntax:**
The benchmark uses modern features like `const` (const declaration), template literals (`\r\n` in the script preparation code is not used, but this example shows its usage), and array destructuring (`Array(length)`). These features are part of ECMAScript 2015 (ES6) syntax.

**Alternatives:**
Other ways to create arrays could be tested, such as:

* Using `Math.pow()` or other numerical methods to calculate the desired size
* Using a library like Lodash or Underscore.js for array creation and manipulation
* Using a different approach altogether, like using an array buffer or a typed array

However, these alternatives may not provide meaningful results or are already covered by existing benchmarks.

Overall, this benchmark provides a comprehensive comparison of various methods for creating and filling arrays in JavaScript, covering both modern and traditional approaches.

Related benchmarks:

Create New Array & Fill it (version: 0)

Comparing performance of: Map vs Array.apply + Fill vs While Loop vs For Loop vs New Array + Fill vs Array Literal With Length + Fill

Created: 3 years ago by: Guest

Jump to the latest result

Map

Array.apply + Fill

While Loop

For Loop

New Array + Fill

Array Literal With Length + Fill

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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