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: one year 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

Test name	Executions per second
let	36.7 Ops/sec
var	37.2 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.

Related benchmarks:

let vs var for loop 233 (version: 0)

let vs var for loop

Comparing performance of: let vs var

Created: 3 years ago by: Guest

Jump 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):