Benchmark: var let test - MeasureThat.net

Tests:

var
var sum = 0; for (var i = 0; i < 100; i++) { for (var j = 0; j < 100; j++) { sum += j; if (sum > 10000) { sum = 0; } } };
let
let sum = 0; for (let i = 0; i < 100; i++) { for (let j = 0; j < 100; j++) { sum += j; if (sum > 10000) { sum = 0; } } };

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: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36

Browser/OS: Chrome 100 on Windows

View result in a separate tab

Test name	Executions per second
var	169390.0 Ops/sec
let	170200.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the provided benchmark.

**Benchmark Overview**

The benchmark is designed to compare the performance of two variables in JavaScript: `var` and `let`. The test cases are simple loops that increment a variable (`sum`) within a nested loop structure. The goal is to measure which variable performs better in terms of execution speed.

**Options Compared**

There are two options being compared:

1. **`var`**: The traditional JavaScript keyword for declaring variables, introduced in ECMAScript 1999.
2. **`let`**: A newer keyword introduced in ECMAScript 2015 (ES6) to declare block-scoped variables.

**Pros and Cons**

### `var`

Pros:

* Widespread support across browsers and older JavaScript versions
* Simple to use and understand

Cons:

* `var` is function-scoped, which means it can "leak" into surrounding scopes, leading to unexpected behavior.
* The variable's scope is determined by the nearest enclosing function or global scope, rather than being explicitly declared.

### `let`

Pros:

* Block-scoped, meaning its scope is limited to the block it's declared within (e.g., loops, if-else statements).
* Avoids "leakage" into surrounding scopes.
* Introduced in ES6, so it's a more modern and explicit way of declaring variables.

Cons:

* Requires support for ES6 syntax and modern browsers.
* Can lead to confusion if not understood correctly.

**Other Considerations**

The benchmark also considers the use of `const`, which is another keyword introduced in ES6. However, since there are no test cases that explicitly use `const`, it's not considered in this comparison.

**Library/Functionality Used**

There doesn't seem to be any specific library or functionality used in this benchmark beyond the JavaScript variables being compared.

**Special JS Features/Syntax**

The benchmark uses the following ES6 features:

* Let and var declarations
* Block-scoped variable declarations
* For loops

These features are supported by most modern browsers, including Chrome 100, which is used in the benchmark.

**Other Alternatives**

If you're interested in exploring alternative JavaScript variables or scoping mechanisms, some alternatives include:

* `const`: A keyword introduced in ES6 for declaring constant variables.
* `let` and `const` with `var` (not recommended)
* Arrow functions (`=>`) for creating concise functions
* Classes and object-oriented programming for encapsulating data and behavior

Related benchmarks:

var let test (version: 0)

Comparing performance of: var vs let

Created: 2 years ago by: Guest

Jump to the latest result

var

let

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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