Benchmark: Cashing length of array

Tests:

NOT cashing array length
var arr = Array.from({length: 500}, (i,x) => x); for (var i = 0; i < arr.length; ++i) { arr[i] += 1; }
Cashing array length
var arr = Array.from({length: 500}, (i,x) => x); for (var i = 0, len = arr.length; i < len; ++i) { arr[i] += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
NOT cashing array length
Cashing array length

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 its test cases.

**Benchmark Overview**

The benchmark measures the performance of JavaScript arrays, specifically comparing two approaches: "NOT cashing array length" and "Cashing array length".

**Script Preparation Code**

There is no script preparation code provided in the Benchmark Definition JSON. This means that the browser will execute a minimal amount of setup code before running each test case.

**Individual Test Cases**

There are only two test cases:

1. **NOT cashing array length**: In this test, a new Array.from() call creates an array with 500 elements and assigns it to the `arr` variable. The loop then increments each element in the array using `arr[i] += 1;`. This approach does not cache the length of the array.
2. **Cashing array length**: In this test, a new Array.from() call creates an array with 500 elements and assigns it to the `arr` variable. The loop then increments each element in the array using `arr[i] += 1;`, but instead of accessing the `length` property directly (`i < len;`), a cached value is used (`len`). This approach caches the length of the array.

**Library and Purpose**

There are no libraries explicitly mentioned in the provided code. However, it's worth noting that Array.from() is a built-in JavaScript method introduced in ECMAScript 2015 (ES6). It creates a new array from an iterable or an array-like object.

**Special JS Feature/Syntax**

This benchmark does not use any special JavaScript features or syntax.

**Pros and Cons of Different Approaches**

1. **NOT cashing array length**:
	* Pros: Simple, straightforward approach that doesn't require caching the array's length.
	* Cons: Potentially slower due to repeated access to `arr.length`.
2. **Cashing array length**:
	* Pros: Caching the array's length can reduce the number of accesses and improve performance.
	* Cons: Requires additional memory to store the cached value, which may be a concern for large arrays.

**Other Alternatives**

If you're interested in optimizing JavaScript array performance, here are some alternative approaches:

1. **Using `Array.prototype.slice()`**: Instead of using Array.from(), you can create an array by slicing a new instance of Array from an existing array.
2. **Preallocating memory**: You can preallocate memory for your array using the `new Float64Array(size)` constructor (for floating-point numbers) or `new Uint8Array(size)` constructor (for integers).
3. **Using typed arrays**: If you know the type and size of your data, consider using typed arrays like Int32Array, Float64Array, etc.
4. **Minimizing array accesses**: Try to minimize the number of times you access an array's elements or its length.

Keep in mind that these alternatives may require additional setup code and might not always improve performance.

Related benchmarks:

Cashing length of array (version: 0)

Comparing performance of: NOT cashing array length vs Cashing array length

Created: 7 years ago by: Guest

Jump to the latest result

NOT cashing array length

Cashing array length

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):