Benchmark: var vs const vs let

Tests:

var
var g = 1; var c = g + 1;
let
let g = 1; let c = g + 1;
const
const g = 1; const c = g + 1;

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 runs

let

145.9M/s

var

141.6M/s

const

141.3M/s

View exact numbers

✓ let: 145,871,360 ops/sec
• var: 141,633,904 ops/sec
• const: 141,311,856 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
var
let
const

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Mac OS X 10.15.7

View result in a separate tab

let

171.9M/s

const

167.5M/s

var

161.8M/s

View exact numbers

Test name	Executions per second
✓ let	171,858,336 Ops/sec
const	167,463,536 Ops/sec
var	161,777,616 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmarking test case on the MeasureThat.net website. The benchmark compares the performance of three JavaScript variable declarations: `var`, `const`, and `let`.

**Variable Declaration Options**

1. **`var`**: The traditional JavaScript variable declaration, which declares a variable that can be reassigned.
	* Pros:
		+ Wide support across older browsers.
	* Cons:
		+ Can lead to performance issues due to hoisting and reassignment.
2. **`const`**: A more modern JavaScript variable declaration, which declares a constant that cannot be reassigned after initialization.
	* Pros:
		+ Improved code readability and maintainability.
		+ Better performance compared to `var`.
3. **`let`**: Another modern JavaScript variable declaration, which declares a block-scoped variable that can be reassigned.
	* Pros:
		+ Similar syntax to `const`, making it easier to read and write code.
		+ Good performance.

**Comparison**

The benchmark compares the execution times of each variable declaration option in a simple assignment scenario:

```javascript
var g = 1;
var c = g + 1;
```

The test cases also include variants with `let` and `const`, which can help identify performance differences between these options.

**Library Usage**

None of the test cases use any JavaScript libraries. The benchmark focuses solely on comparing the native variable declaration options.

**Special JS Features or Syntax**

There are no special JavaScript features or syntax used in this benchmark.

**Other Alternatives**

If you wanted to compare other JavaScript variable declaration options, such as:

* **`let const`**: A more modern alternative to `var`, which combines the benefits of `const` and `let`.
* **`class-based variables`**: Some newer JavaScript engines support class-based variables, which can provide better scoping and memory management.

However, these alternatives are not currently supported by MeasureThat.net.

var vs const vs let (version: 1)

Comparing performance of: `var vs let vs const`

Created: 2 years ago by: Registered User

Go to the latest result

var

let

const

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 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 vs const vs let (version: 1)

Comparing performance of: var vs let vs const

Created: 2 years ago by: Registered User

Go to the latest result

var

let

const

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 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: `var vs let vs const`