Benchmark: const vs let vs var - proper

Tests:

var
var g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()
let
let g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()
const
const g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()

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/111.0.0.0 Safari/537.36

Browser/OS: Chrome 111 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
var	37343204.0 Ops/sec
let	26285448.0 Ops/sec
const	10785087.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided JSON represents a benchmark test case comparing the performance of three JavaScript variables: `var`, `let`, and `const`. The benchmark measures how long it takes for each variable to execute a specific piece of code, which involves creating an array and pushing some values into it.

**Options compared:**

*   **`var`**: The `var` keyword is used to declare variables that have function scope. In the test case, `g` is declared as a `var` variable.
*   **`let`**: The `let` keyword is used to declare variables that have block scope. In the test case, `g` is declared as a `let` variable.
*   **`const`**: The `const` keyword is used to declare variables that have block scope and cannot be reassigned. In the test case, `g` is declared as a `const` variable.

**Pros and Cons of each approach:**

*   **`var`**: Variables declared with `var` have function scope, which means they are accessible throughout the entire function where they are defined. However, this also means that they can be overwritten by subsequent assignments in the same scope.
    *   **Pros:** Simple to use and understand.
    *   **Cons:** Can lead to unexpected behavior due to variable hoisting (variables are "hoisted" to the top of their scope).
*   **`let`**: Variables declared with `let` have block scope, which means they can only be accessed within the block where they are defined. This helps prevent variables from being overwritten by subsequent assignments in the same scope.
    *   **Pros:** Blocks the variable's scope to a specific region of code.
    *   **Cons:** May lead to confusing code if not used carefully.
*   **`const`**: Variables declared with `const` have block scope, similar to `let`. However, they cannot be reassigned once they are initialized. This provides additional protection against accidental changes to variables.
    *   **Pros:** Provides a high degree of security and predictability when working with variables.
    *   **Cons:** Can lead to more verbose code if used unnecessarily.

**Library usage:**

There is no explicit library usage in the provided benchmark test case. However, it's worth noting that some JavaScript implementations, like V8 (used by Chrome), have additional features and optimizations for certain types of variables.

**Special JS feature or syntax:**

This benchmark does not use any special JavaScript features or syntax beyond what is standard in modern JavaScript.

Related benchmarks:

const vs let vs var - proper (version: 0)

Comparing performance of: var vs let vs const

Created: one year ago by: Guest

Jump to the latest result

var

let

const

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):