Benchmark: var-let-const20 - MeasureThat.net

Script Preparation code:

function functionConst(arg) {
	const obj = {};
  	obj.fn = () => console.log(obj, arg);
  return obj;
}
function functionVar(arg) {
	var obj = {};
  	obj.fn = () => console.log(obj, arg);
  return obj;
}
 
function functionLet(arg) {
	let obj = {};
  	obj.fn = () => console.log(obj, arg);
  return obj;

}

Tests:

const
functionConst(Math.random())
let
functionLet(Math.random())
var
functionVar(Math.random())

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Other 5 runs

let

12.1M/s

const

12.0M/s

var

11.9M/s

View exact numbers

✓ let: 12,055,107 ops/sec
• const: 12,020,142 ops/sec
• var: 11,913,219 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
const
let
var

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/129.0.0.0 Safari/537.36

Browser/OS: Chrome 129 on Windows

View result in a separate tab

let

9.8M/s

var

9.6M/s

const

9.6M/s

View exact numbers

Test name	Executions per second
✓ let	9,819,665 Ops/sec
var	9,630,361 Ops/sec
const	9,602,191 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the benchmark.

**What is being tested?**

The provided JSON represents a microbenchmark that tests the performance difference between three JavaScript variable declarations: `const`, `let`, and `var`. The test measures the execution time of a simple function, `functionConst`, `functionLet`, and `functionVar`, which returns an object with a logging method. Each function takes a random value as an argument.

**Options being compared**

The three options being compared are:

1. **`const`**: A variable declaration that declares a constant variable, which cannot be reassigned.
2. **`let`**: A variable declaration that declares a mutable variable, which can be reassigned.
3. **`var`**: A variable declaration that declares a global or function-scoped variable, which can be accessed from anywhere in the code.

**Pros and Cons of each approach**

1. **`const`**:
	* Pros: Memory usage is optimized since the value cannot be changed, resulting in better performance for large datasets.
	* Cons: The variable must be initialized with a value before it's used, which can lead to errors if not done correctly.
2. **`let`**:
	* Pros: Easier to use than `var`, as it eliminates global scope issues.
	* Cons: Memory usage is optimized only for the block scope of the variable declaration.
3. **`var`**:
	* Pros: Wide compatibility and support across older browsers.
	* Cons: Global or function-scoped variables can lead to naming conflicts and are not suitable for modern JavaScript development.

**Library and its purpose**

None of the test cases use any external libraries. The functions `functionConst`, `functionLet`, and `functionVar` only rely on built-in JavaScript features.

**Special JS feature or syntax**

There is no special JavaScript feature or syntax being used in this benchmark.

**Other considerations**

* The test environment uses a desktop browser (Opera 113) to ensure consistency across different platforms.
* The benchmark measures the execution time of each function, which can be affected by other factors such as memory allocation and garbage collection.
* The use of `Math.random()` generates random values for testing purposes.

**Alternatives**

Other alternatives to measure the performance of variable declarations could include:

1. Using a more modern JavaScript feature like `let` or `const` with a large dataset.
2. Comparing the performance of different compilers or transpilers (e.g., Babel).
3. Investigating the impact of variable declaration scope on performance using techniques like hoisting.
4. Adding additional factors, such as caching or lazy loading, to measure their effect on performance.

Keep in mind that these alternatives may require modifications to the benchmark setup and test cases to ensure accurate results.

var-let-const20 (version: 2)

Comparing performance of: `const vs let vs var`

Created: one year ago by: Registered User

Go to the latest result

const

let

var

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Other 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

var-let-const20 (version: 2)

Comparing performance of: const vs let vs var

Created: one year ago by: Registered User

Go to the latest result

const

let

var

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Other 5 runs

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: `const vs let vs var`