Benchmark: grthyvar vs let vs const

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

let arr = Array(30).fill(()=>{})

Tests:

var
for(var o of arr) o()
let
for(let o of arr) o()
const
for(const o of arr) o()
outside - var
var o for(o of arr) o()
outside - let
let o for(o of arr) o()
global
for(o of arr) o()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
var
let
const
outside - var
outside - let
global

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36 OPR/87.0.0.0

Browser/OS: Opera 87 on Android

View result in a separate tab

Test name	Executions per second
var	8386393.0 Ops/sec
let	8886152.0 Ops/sec
const	8777386.0 Ops/sec
outside - var	8873713.0 Ops/sec
outside - let	8802235.0 Ops/sec
global	65922.8 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 months ago):

LLMs can make mistakes. Check important info.

### Benchmark Overview

This benchmark compares the performance of different variable declaration mechanisms in JavaScript: `var`, `let`, and `const`. Additionally, it tests the performance of these declarations when they are defined inside a loop versus when defined outside. The tests' execution is set up with an array filled with 30 arrow functions.

### Test Cases

1. **Variable Declarations**
   - **`var`**: Traditional declaration allowing redeclaration and hoisting.
   - **`let`**: Block-scoped declaration that does not allow redeclaration within the same scope and is not hoisted like `var`.
   - **`const`**: Also block-scoped, but it prevents reassignment after its initial assignment.

2. **Outside Definitions**
   - **`outside - var`**: The `var` is defined outside the loop, iterating over the array and invoking each function.
   - **`outside - let`**: Similar to the above, but with `let`.
  
3. **Global Declaration**
   - **`global`**: This case refers to a variable defined in the global scope that is used to iterate over the array.

### Results Interpretation

The benchmark results indicate the number of executions per second for different implementation methods. Here are the results for insights:

- **`var` achieved the highest performance** with approximately 9,624,945 executions per second.
- **`const` is a close second** at 9,574,107 executions per second.
- **`outside - var` and `let`** performed similarly but were slightly lower than `const`.
- **`global` is significantly slower** than all other cases, achieving only about 124,162 executions per second. This drastic reduction can be attributed to the overhead of using a global scope, which is generally less optimized compared to local scopes.

### Pros and Cons of Each Approach

1. **`var`**
   - **Pros**: 
     - Allowance for redeclaration can simplify scope management under certain conditions.
     - Hoisted to the top within the function scope, making it available before its declaration.
   - **Cons**: 
     - Hoisting can lead to difficult-to-debug scenarios, such as unexpected values being used before the assignment.

2. **`let`**
   - **Pros**: 
     - Block-scoped, reducing potential clashes with variable names.
     - Prevents redeclaration in the same scope, providing safer code.
   - **Cons**: 
     - Slightly less performant in certain contexts compared to `var` due to its block-scoping overhead.

3. **`const`**
   - **Pros**: 
     - Ensures that variables can't be reassigned, which is great for maintaining immutability where needed.
     - Also block-scoped, reducing errors related to variable reference.
   - **Cons**: 
     - Its restriction can lead to verbosity if some values need reassignment.

4. **Outside Declaration vs. Inside Declaration**
   - **Pros**: 
     - Declaring a variable outside of the loop can make it available for further use, improving readability and scope management.
   - **Cons**: 
     - Performance differences were noted, potentially decreasing execution speed (especially with global scope defined variables).

### Considerations

When comparing these declarations, it's important to consider the context of their use:
- In modern JavaScript development, `let` and `const` have become preferred due to their more predictable behaviors with block-scoping and immutability. 
- Performance might be more critical in compute-intensive applications, although in most cases, focusing on readability and maintainability takes precedence.
- Avoiding global variables is a standard good practice as they can lead to issues in larger codebases due to scope complexity.

### Alternatives

Other alternatives for variable declaration include using:
- **Functional Scoped Variables**: Using function forms can encapsulate variables to avoid clashes altogether.
- **Static Type Checkers** (e.g., TypeScript) can help manage variable types and scopes in a more controlled way than standard JavaScript provides.
- **Modules**: ES6 modules can scope variables to the module level, preventing conflicts with other script files.

In conclusion, the performance implications, while crucial, should harmoniously align with the principles of maintainable and clean code practices.

Related benchmarks:

grthyvar vs let vs const (version: 1)

Comparing performance of: var vs let vs const vs outside - var vs outside - let vs global

Created: 2 months ago by: Guest

Jump to the latest result

var

let

const

outside - var

outside - let

global

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 months ago):