Benchmark: var vs let vs const v2

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

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Measuring the performance of JavaScript variables is an essential aspect of understanding how different languages handle memory management and execution speed.

The provided JSON represents a benchmark that tests the performance of three types of JavaScript variables: `var`, `let`, and `const`. These variables have different scoping behavior, which affects how they are executed and stored in memory.

**Options being compared:**

1.  **`var`**: The traditional variable declaration method in JavaScript. Variables declared with `var` have function scope, meaning their value is scoped to the entire function it's defined within.
2.  **`let`**: A block-scoped variable declaration method introduced in ES6. `let` variables are only accessible within the block they're declared in (e.g., a loop or an if statement).
3.  **`const`**: A block-scoped constant declaration method also introduced in ES6. Like `let`, `const` variables are only accessible within their defined scope.

**Pros and Cons of each approach:**

*   **`var`**:
    *   **Pros:** More compatible with older browsers, has a simpler syntax.
    *   **Cons:** Can lead to unexpected behavior due to variable hoisting (moving declarations to the top of their scope) and global scope issues.

*   **`let`**: Offers better readability and maintainability than `var`. It's also more efficient in modern JavaScript engines because it allows for better optimization by not having side effects.
    *   **Pros:** Improved code readability, reduces common pitfalls like variable hoisting, easier to reason about variable scope.
    *   **Cons:** Requires support for ES6 syntax and may require additional setup if you're working with older browsers.

*   **`const`**: Adds a way to declare constants that can't be reassigned, making the code more robust and preventing unexpected changes.
    *   **Pros:** Better suited for variables that don't need to change during their lifetime, prevents accidental mutations of values declared as constants, makes the code easier to reason about.
    *   **Cons:** Similar to `let`, requires ES6 support.

**Special JavaScript features used:**

None mentioned explicitly in this benchmark. However, it's worth noting that modern JavaScript engines like V8 (used by Chrome) and SpiderMonkey (used by Firefox) have various optimizations and optimizations for performance, such as:

*   **Just-In-Time (JIT) compilation:** Compiles frequently executed code into native machine code.
*   **Garbage collection:** Manages memory allocation and deallocation to prevent memory leaks.

**Library usage:**

The benchmark doesn't use any external libraries. However, in general, JavaScript benchmarks might rely on libraries like:

*   **Benchmark.js**: A widely used library for writing benchmarks.
*   **Jest-Benchmark**: For running JavaScript benchmarks using Jest framework.

**Special JS features/syntax (if applicable):**

This benchmark specifically mentions the introduction of `let` and `const` in ES6, which introduced block-scoped variables. These changes are a significant improvement over traditional variable declarations like `var`, making code more readable and maintainable while also enabling better optimization by JavaScript engines.

**Alternatives:**

If you're looking for alternatives to MeasuringThat.net, consider:

*   **Benchmark.js**: As mentioned earlier, it's widely used for writing benchmarks.
*   **JSPerf.com**: A popular platform for running JavaScript performance tests and benchmarking different implementations of JavaScript features.
*   **Google Benchmark**: A lightweight framework for benchmarking C++ code but can also be applied to JavaScript using Node.js or browser environments.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.5112.20 Safari/537.36

Browser/OS: Chrome 104 on Windows

View result in a separate tab

Test name	Executions per second
var	1114581.2 Ops/sec
let	1258370.6 Ops/sec
const	1235477.9 Ops/sec

Related benchmarks:

var vs let vs const v2 (version: 0)

Comparing performance of: var vs let vs const

Created: 2 years ago by: Registered User

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 26 days ago):