Benchmark: let vs var for loop 233

Tests:

let
const styles = Array.apply(null, {length: 100000}).map(Number.call, Number) for (let i in styles) {}
var
const styles = Array.apply(null, {length: 100000}).map(Number.call, Number) for (var i in styles) {}

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
let
var

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 124 on Android

View result in a separate tab

var

37/s

let

37/s

View exact numbers

Test name	Executions per second
✓ var	37 Ops/sec
let	37 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

**What is being tested:**

The benchmark compares the performance of two approaches for iterating over an array using `for` loops:

1. **`let` loop**: The first test case uses the `let` keyword to declare a variable `i` that is scoped to the block.
2. **`var` loop**: The second test case uses the `var` keyword to declare a variable `i` that has function scope.

**Options compared:**

The benchmark compares two options:

1. **Using `let` or `var` for loop**: This option tests which approach is faster when iterating over an array using a `for` loop.
2. **`Array.apply` and `Number.call`**: This option tests how these methods are used to create an array of numbers (in this case, 100,000 times) before the loop.

**Pros and Cons:**

* Using `let` or `var` for loop:
	+ Pros:
		- `let` loops are more modern and easier to read, but may have performance overhead due to block scoping.
		- `var` loops are more traditional and can be faster, but may lead to unexpected behavior with variable hoisting.
	+ Cons:
		- Performance differences between `let` and `var` loops can vary depending on the specific use case.
* Using `Array.apply` and `Number.call`:
	+ Pros:
		- These methods provide a convenient way to create an array of numbers, especially when working with legacy code or older JavaScript versions.
	+ Cons:
		- These methods are often slower than more modern approaches, such as using the spread operator (`[...array].map()`).

**Library:**

There is no specific library being tested in this benchmark. However, it's worth noting that `Array.apply` and `Number.call` are part of the JavaScript standard library.

**Special JS feature or syntax:**

This benchmark does not use any special JavaScript features or syntax beyond what's covered in the standard library.

**Benchmark preparation code:**

The script preparation code is empty (`null`), which means that the benchmark starts from a clean slate. This allows for more accurate comparisons between different approaches.

**Other alternatives:**

To test this same scenario, you could consider using other approaches, such as:

1. Using `for...of` loops instead of traditional `for` loops.
2. Comparing the performance of `let`, `const`, and `var` variables in general.
3. Testing the impact of array iteration methods like `forEach()`, `map()`, or `filter()` on performance.

These alternatives would require modifications to the benchmark definition and script preparation code, but could provide more comprehensive insights into JavaScript performance optimization techniques.

let vs var for loop 233 (version: 0) Benchmark.js

let vs var for loop

Comparing performance of: `let vs var`

Created: 3 years ago by: Guest

Go to the latest result

let

var

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

let vs var for loop 233 (version: 0) Benchmark.js

let vs var for loop

Comparing performance of: let vs var

Created: 3 years ago by: Guest

Go to the latest result

let

var

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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