Benchmark: Var vs Let - MeasureThat.net

Tests:

var
for(var i=1;i<=1000;i++) console.log(i);
let
for(let i=1;i<=1000;i++) console.log(i);

Historical Performance Data aggregated from 48 community runs

Desktop Results:

Chrome 23 runs

var

303/s

let

296/s

View exact numbers

✓ var: 303 ops/sec
• let: 296 ops/sec

Firefox 13 runs

var

234/s

let

234/s

View exact numbers

✓ var: 234 ops/sec
• let: 234 ops/sec

Other 6 runs

var

391/s

let

388/s

View exact numbers

✓ var: 391 ops/sec
• let: 388 ops/sec

Mobile Results:

Chrome 6 runs

let

83/s

var

81/s

View exact numbers

✓ let: 83 ops/sec
• var: 81 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

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 months ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_7 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.3 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 26 on iOS 18.7

View result in a separate tab

var

3K/s

let

3K/s

View exact numbers

Test name	Executions per second
✓ var	2,802 Ops/sec
let	2,610 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 benchmark and explain what's being tested.

**Overview**

The benchmark measures the performance difference between using `var` and `let` variables in a for loop, specifically logging numbers from 1 to 1000. The test is designed to evaluate which approach (variable scope) results in faster execution.

**Variables: Var vs Let**

In JavaScript, both `var` and `let` are used as variable declarations, but they behave differently when it comes to scoping:

* **Var**: Variables declared with `var` have function scope, not block scope. This means that a single variable declaration can affect variables from outer scopes within the same function.
* **Let**: Variables declared with `let` have block scope, which means each variable is scoped to its own block (e.g., if statement, loop, or switch). This provides better isolation and avoids polluting the global scope.

**Performance Comparison**

The test compares the performance of two code snippets:

1. Using `var` for loop:
```javascript
for(var i=1;i<=1000;i++) console.log(i);
```
2. Using `let` for loop:
```javascript
for(let i=1;i<=1000;i++) console.log(i);
```

**Pros and Cons**

* **Var**: The main advantage of using `var` is that it might be faster in older browsers or environments where `let` support was not yet implemented. However, this comes at the cost of potential variable scope issues.
* **Let**: Using `let` provides better code maintainability, as variables are isolated and less likely to pollute outer scopes.

In most modern JavaScript environments, `let` is preferred over `var` due to its block scope behavior.

**Special JS Features/Syntax**

There's no special feature or syntax being tested in this benchmark. It solely focuses on comparing the performance of `var` vs `let`.

**Other Alternatives**

If you want to explore more JavaScript performance benchmarks, here are some alternatives:

* MeasureThat.net: Offers various benchmarks for JavaScript engines.
* Browser Benchmark: Provides a range of browser-specific benchmarks.
* jsperf (now archived): Was an older benchmarking platform that compared different aspects of JavaScript.

Keep in mind that benchmarking results may vary depending on the specific environment, hardware, and JavaScript engine used. Always verify results with multiple tests and sources to ensure accuracy.

Var vs Let (version: 0)

Just a simple test with var/let performance in for loop

Comparing performance of: `var vs let`

Created: 9 years ago by: Guest

Go to the latest result

var

let

Historical Performance Data aggregated from 48 community runs

Desktop Results:

Chrome 23 runs

Firefox 13 runs

Other 6 runs

Mobile Results:

Chrome 6 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 Let (version: 0)

Just a simple test with var/let performance in for loop

Comparing performance of: var vs let

Created: 9 years ago by: Guest

Go to the latest result

var

let

Historical Performance Data aggregated from 48 community runs

Desktop Results:

Chrome 23 runs

Firefox 13 runs

Other 6 runs

Mobile Results:

Chrome 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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Comparing performance of: `var vs let`