Benchmark: const vs let vs var fork

Tests:

var
var g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()
let
let g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()
const
const g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
var
let
const

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.3.1 Safari/605.1.15

Browser/OS: Safari 17 on Mac OS X 10.15.7

View result in a separate tab

let

15.6M/s

var

15.4M/s

const

15.1M/s

View exact numbers

Test name	Executions per second
✓ let	15,634,461 Ops/sec
var	15,382,945 Ops/sec
const	15,121,953 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 Definition**

The benchmark defines three test cases:

1. `var g = { e: [] }\r\ng.o = function(x) { g.e.push(...[1,2,3]) }\r\ng.o()`
2. `let g = { e: [] }\r\ng.o = function(x) { g.e.push(...[1,2,3]) }\r\ng.o()`
3. `const g = { e: [] }\r\ng.o = function(x) { g.e.push(...[1,2,3]) }\r\ng.o()`

These test cases create an object `g` with a property `e`, which is initialized as an empty array. Then, a function `g.o()` is defined that pushes three elements to the `e` array.

**What's being tested?**

The benchmark is comparing the performance of three different variable declarations: `var`, `let`, and `const`. Specifically, it's measuring how fast each declaration can execute the code inside the function call.

**Options compared**

In JavaScript, there are two ways to declare variables:

1. **Function scope**: Variables declared with `var` have a function scope, which means they're accessible only within the function where they're defined.
2. **Block scope**: Variables declared with `let` and `const` have a block scope, which means they're accessible only within the block (e.g., `{}`) where they're defined.

The benchmark is comparing the performance of:

* `var g = { e: [] }` (function scope)
* `let g = { e: [] }` (block scope)
* `const g = { e: [] }` (block scope)

**Pros and cons**

Here are some pros and cons for each variable declaration approach:

* **Var**:
	+ Pros: No additional syntax or declarations needed.
	+ Cons: Can lead to variables being accessed outside their intended scope, causing bugs.
* **Let**:
	+ Pros: Block scope is more predictable and easier to understand than function scope. Less likely to introduce bugs due to variable hoisting.
	+ Cons: Requires additional syntax (`let`) and may require explicit re-declarations if the block scope changes.
* **Const**:
	+ Pros: Ensures variables are not modified after declaration, reducing bugs related to mutable state.
	+ Cons: May require more code changes if a variable's value needs to be updated.

**Library and special JS features**

There are no libraries or special JavaScript features used in this benchmark. The tests rely on standard JavaScript syntax and behavior.

**Alternative approaches**

If you're looking for alternative approaches, here are some options:

* **Use a testing framework**: Tools like Jest or Mocha can help you write and run more complex benchmarks.
* **Experiment with different execution environments**: You could test your code in different browsers, Node.js versions, or environments to identify platform-specific performance differences.
* **Consider parallelization**: If you have multiple variables being compared, you might want to test them simultaneously to reduce overall benchmarking time.

Keep in mind that the choice of variable declaration approach ultimately depends on the specific requirements and constraints of your project.

const vs let vs var fork (version: 0)

Comparing performance of: `var vs let vs const`

Created: 2 years ago by: Guest

Go to the latest result

var

let

const

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

const vs let vs var fork (version: 0)

Comparing performance of: var vs let vs const

Created: 2 years ago by: Guest

Go to the latest result

var

let

const

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `var vs let vs const`