Benchmark: Array for vs. map push

Script Preparation code:

var arr = new Array(10000).fill(null);

Tests:

for
for (let i = 0; i < arr.length; i++) { arr[i] = i; }
optimized for
for (let i = 0, l = arr.length; i < l; i++) { arr[i] = i; }
includes
arr = arr.map((v, i) => v = i);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
optimized for
includes

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark is comparing three different ways to assign values to an array of 10,000 elements:

1. **Original "for" loop**: `for (let i = 0; i < arr.length; i++) {\r\n  arr[i] = i;\r\n}`
2. **Optimized "for" loop**: `for (let i = 0, l = arr.length; i < l; i++) {\r\n  arr[i] = i;\r\n}`
3. **Array method: map() with assignment**: `arr = arr.map((v, i) => v = i);`

**Approaches Compared**

The three approaches are compared in terms of execution speed.

* The original "for" loop uses a traditional loop structure to iterate over the array and assign values.
* The optimized "for" loop uses a more concise syntax to initialize variables within the loop, which can potentially lead to faster execution.
* The Array method: map() with assignment uses the built-in map() function to create a new array with transformed elements. However, in this case, it's used with an assignment operator instead of the traditional return value.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **Original "for" loop**:
	* Pros: Easy to understand and maintain.
	* Cons: May be slower due to the explicit loop structure.
2. **Optimized "for" loop**:
	* Pros: Can be faster due to the concise syntax, but may be harder to read for those not familiar with this syntax.
	* Cons: Syntax can be less intuitive, and may lead to errors if not used correctly.
3. **Array method: map() with assignment**:
	* Pros: Uses built-in functions that are optimized for performance.
	* Cons: May require an understanding of the map() function and its limitations in this context.

**Library Used**

In the "optimized for" loop, a variable `l` is used to store the length of the array. This is not a specific library but rather a common JavaScript technique to avoid repeating the `arr.length` expression within the loop.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntaxes being tested in this benchmark. However, it's worth noting that some modern JavaScript engines and transpilers (e.g., Babel) may optimize or transform certain code patterns, including those used in the optimized "for" loop.

**Alternatives**

If you're looking for alternatives to these approaches, here are a few options:

1. **Using a traditional for loop with early exit**: Instead of iterating over the entire array, consider using an early exit condition to stop the iteration as soon as a certain condition is met.
2. **Using a more modern approach: reduce() or spread()**: If you need to transform an array in-place, consider using functions like `reduce()` or `spread()`, which can provide a more concise and expressive way of doing so.
3. **Using a library like Lodash**: If you need to perform complex array transformations or manipulations, consider using a library like Lodash, which provides a wide range of utility functions for working with arrays.

In summary, this benchmark is testing the performance difference between three different approaches to assigning values to an array of 10,000 elements. The optimized "for" loop and Array method: map() with assignment are compared against the original "for" loop. While the optimized "for" loop may be faster due to its concise syntax, it's essential to consider readability and maintainability when choosing a coding approach.

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36

Browser/OS: Chrome 77 on Windows

View result in a separate tab

Test name	Executions per second
for	850.5 Ops/sec
optimized for	1609.1 Ops/sec
includes	13126.6 Ops/sec

Related benchmarks:

Array for vs. map push (version: 0)

Comparing performance of: for vs optimized for vs includes

Created: 5 years ago by: Guest

Jump to the latest result

for

optimized for

includes

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):