Benchmark: var-let-const4 - MeasureThat.net

Script Preparation code:

function withConst(a,b) {
	const x = a + '10';
  	return x + b;
}

function withLet(a,b) {
	let x = a + '10';
  	return x + b;
}

function withVar(a,b) {
	var x = a + '10';
  	return x + b;
}

Tests:

const
withConst(Math.random(), Math.random())
let
withLet(Math.random(), Math.random())
var
withVar(Math.random(), Math.random())

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

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases.

**Benchmark Definition JSON**

The benchmark definition JSON represents a JavaScript microbenchmark that measures the performance of three different variable declarations: `const`, `let`, and `var`. The script preparation code defines three functions, each with a similar structure:

*   `withConst(a, b)`: declares a constant variable `x` using the `const` keyword and returns its value plus `b`.
*   `withLet(a, b)`: declares a variable `x` using the `let` keyword and returns its value plus `b`.
*   `withVar(a, b)`: declares a variable `x` using the `var` keyword and returns its value plus `b`.

The HTML preparation code is not provided, which suggests that it's not necessary for this benchmark.

**Individual Test Cases**

Each test case represents a variation of the benchmark definition. The test cases are:

*   **const**: uses the `withConst(Math.random(), Math.random())` function definition.
*   **let**: uses the `withLet(Math.random(), Math.random())` function definition.
*   **var**: uses the `withVar(Math.random(), Math.random())` function definition.

**Options Compared**

The benchmark compares the performance of three different variable declarations: `const`, `let`, and `var`. The options are:

*   **const**: uses the `const` keyword to declare a constant variable.
*   **let**: uses the `let` keyword to declare a variable that is scoped to its block (i.e., it's not accessible outside of that block).
*   **var**: uses the `var` keyword to declare a variable that is function-scoped (i.e., it's accessible throughout the entire function).

**Pros and Cons of Each Approach**

Here are some pros and cons of each approach:

*   **const**:
    *   Pros: constant variables are evaluated only once, at compile-time. This can lead to better performance, as there is no reevaluation overhead.
    *   Cons: constants cannot be reassigned; if you need to change the value later, you'll have to use a variable instead.
*   **let**:
    *   Pros: variables are scoped to their block, which helps prevent polluting the global namespace. This can make code more readable and maintainable.
    *   Cons: let variables are function-scoped, which means they're not hoisted like var variables. You need to use `let` or `const` instead of just declaring a variable without any keyword.
*   **var**:
    *   Pros: old-school syntax that's easy to read and write for those familiar with the language.
    *   Cons: var variables are function-scoped, which can lead to unexpected behavior when dealing with global scope. This has been largely discouraged in modern JavaScript development.

**Special JS Features or Syntax**

The benchmark does not use any special JS features or syntax that would require explanation beyond the variable declarations and their performance characteristics.

**Other Alternatives**

If you wanted to write a similar benchmark, you could explore other variable declarations, such as:

*   `let` without the function scope (e.g., using ES6 block scope)
*   `const` with dynamic property names
*   Other modern JavaScript features like `class`, `import`, or `export`

You could also add more test cases to cover additional scenarios, such as:

*   Using object literals instead of variables
*   Adding conditional statements or loops
*   Incorporating other performance-critical elements, like DOM manipulation or asynchronous operations

Keep in mind that the goal of a benchmark is to compare the performance of different approaches under controlled conditions. You may need to adjust your approach based on the specific requirements and use cases you're trying to measure.

**Benchmark Preparation Code**

The script preparation code for the benchmark includes three functions, each with similar structure:

```javascript
function withConst(a, b) {
    const x = a + '10';
    return x + b;
}

function withLet(a, b) {
    let x = a + '10';
    return x + b;
}

function withVar(a, b) {
    var x = a + '10';
    return x + b;
}
```

**Benchmark Results**

The benchmark results are provided in the format of an array, where each element represents a test case. The results include:

*   `RawUAString`: the browser's User Agent string
*   `Browser`: the name of the browser used for the benchmark
*   `DevicePlatform`: the type of device (Desktop or Mobile) used for the benchmark
*   `OperatingSystem`: the operating system used for the benchmark
*   `ExecutionsPerSecond`: the number of executions per second measured by the benchmark

For example, one of the test cases shows:

```json
{
    "RawUAString": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36 OPR/113.0.0.0",
    "Browser": "Opera 113",
    "DevicePlatform": "Desktop",
    "OperatingSystem": "Windows",
    "ExecutionsPerSecond": 3729430.0,
    "TestName": "const"
}
```

This result shows that the `const` variable declaration was executed approximately 3,729,430 times per second on a Windows desktop operating system with Opera 113 browser.

Latest run results:

Run details: (Test run date: 3 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36 OPR/113.0.0.0

Browser/OS: Opera 113 on Windows

View result in a separate tab

Test name	Executions per second
const	3729430.0 Ops/sec
let	3374979.0 Ops/sec
var	2928615.0 Ops/sec

Related benchmarks:

var-let-const4 (version: 0)

Comparing performance of: const vs let vs var

Created: 3 months ago by: Guest

Jump to the latest result

const

let

var

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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