Benchmark: variables declare outside or inside loop

Tests:

Outside loop
let value = 0; for (var i = 0; i < 100000000; i++) { value = i % 2; }
Inside Loop
for (var i = 0; i < 100000000; i++) { const value = i % 2; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Outside loop
Inside Loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:134.0) Gecko/20100101 Firefox/134.0

Browser/OS: Firefox 134 on Windows

View result in a separate tab

Test name	Executions per second
Outside loop	18.1 Ops/sec
Inside Loop	17.9 Ops/sec

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 explain what's being tested.

**Benchmark Overview**

The benchmark is designed to compare the performance of JavaScript variables declared outside versus inside loops. The script preparation code is empty, which means that the variable declarations are not explicitly written in the script itself. Instead, the benchmark relies on the user to write a test script with a specific loop structure.

**Variable Declaration Approaches**

There are two approaches being compared:

1. **Declaring variables outside the loop**: In this approach, the variable is declared before the loop using `let` or `var`. The variable's value is then updated within the loop.
2. **Declaring variables inside the loop**: In this approach, the variable is declared directly within the loop using `const`.

**Pros and Cons**

* **Outside Loop Approach**
	+ Pros:
		- Variables are scoped to the outer function or block, which can prevent polluting the global scope.
		- Can be more efficient since the variable is only created once.
	+ Cons:
		- May lead to unexpected behavior due to variable hoisting (var is moved to top of scope).
		- Can result in slower performance due to the need for lookup and redeclaration.
* **Inside Loop Approach**
	+ Pros:
		- Faster performance since the variable can be created immediately within the loop.
		- Less risk of unexpected behavior due to variable hoisting.
	+ Cons:
		- Pollutes the global scope, which can lead to naming conflicts.
		- May result in slower performance if the variable is not cached or reused.

**Library and Special JS Features**

There are no libraries used in this benchmark. However, it's worth noting that JavaScript has some special features like **let`**, `const`, `var`, and `arrow functions`. The `let` and `const` declarations are being tested here, which is a relatively recent addition to the language.

**Test Case Analysis**

The two test cases provided demonstrate the differences between declaring variables outside versus inside loops. The first test case uses `for...of` (outside loop) and creates an array of results, while the second test case uses traditional `for` loops with `const` declarations (inside loop).

In the latest benchmark result, Chrome 119 is reported to have better performance when running the `Inside Loop` approach.

**Alternatives**

Some alternatives to measuring JavaScript performance include:

* **V8's Benchmarking Tool**: A built-in tool in Node.js that allows developers to create and run custom benchmarks.
* **Benchmark.js**: An open-source benchmarking library for JavaScript that provides a simple API for creating and running tests.
* **jsperf**: A popular online benchmarking platform for JavaScript that allows users to compare the performance of different libraries, frameworks, and code snippets.

Keep in mind that these alternatives may have different use cases and requirements compared to MeasureThat.net.

Related benchmarks:

variables declare outside or inside loop (version: 0)

Comparing performance of: Outside loop vs Inside Loop

Created: 3 years ago by: Guest

Jump to the latest result

Outside loop

Inside Loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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