Benchmark: Let vs Const - MeasureThat.net

Tests:

const
const nums = [55, 21, 807, 41, 56, 66, 202]; for(let x = 0, l = nums.length; x < l; ++x) { console.log(nums[x]); }
Var
var nums = [55, 21, 807, 41, 56, 66, 202]; for(var x = 0, l = nums.length; x < l; ++x) { console.log(nums[x]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
const
Var

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark data.

**Benchmark Definition JSON**

The benchmark definition JSON specifies two test cases: `Let vs Const`. This means we're comparing the performance of using `let` and `const` keywords for declaring variables in JavaScript loops.

**Options being compared**

In this benchmark, we have two options:

1. **`let`**: Using the `let` keyword to declare a variable.
2. **`var`**: Using the `var` keyword to declare a variable (note that `var` is considered outdated and should be avoided in modern JavaScript code).

**Pros and Cons of each approach**

* **`let`**:
	+ Pros: More secure, as variables are scoped to their block or function. This can help prevent global variable pollution.
	+ Cons: May incur a small performance penalty due to the redeclaration check (every time `let` is used inside a block).
* **`var`**:
	+ Pros: Generally faster, since it doesn't have the overhead of the redeclaration check.
	+ Cons: More vulnerable to global variable pollution, as variables are global by default.

**Other considerations**

In modern JavaScript, using `const` is generally preferred over `let`, but only when you need to declare a constant value. If you need to reassign a value, use `let`.

In the provided benchmark, we're comparing the performance of `var` and `let` in loops. The results will likely indicate that `let` outperforms `var` due to its scoping benefits.

**Library used**

There doesn't appear to be any external library used in this benchmark.

**Special JS feature or syntax**

This benchmark uses a special JavaScript feature: variable declarations inside loops, specifically with `let` and `var`. This is a common pattern in JavaScript code.

Now, let's look at the individual test cases:

* **Test Case 1: "const"**
	+ Benchmark definition: Using `const` to declare a variable, then logging its value in a loop.
* **Test Case 2: "Var"**
	+ Benchmark definition: Using `var` to declare a variable, then logging its value in a loop.

The latest benchmark results show that Chrome 91 executes the test with `var` faster than the test with `const`.

**Other alternatives**

There are other alternatives for declaring variables in JavaScript loops, such as:

* **Let without initialization**: Using `let` with no initialization.
* **Const without initialization**: Using `const` with no initialization (not recommended).
* **Arrow functions**: Using arrow functions to create anonymous functions, which can simplify variable declarations.

However, these alternatives are not being compared in this benchmark.

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.77 Safari/537.36

Browser/OS: Chrome 91 on Linux

View result in a separate tab

Test name	Executions per second
const	7719.8 Ops/sec
Var	7809.5 Ops/sec

Related benchmarks:

Let vs Const (version: 0)

Comparing performance of: const vs Var

Created: 3 years ago by: Guest

Jump to the latest result

const

Var

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):