Benchmark: const vs let vs var assignment

Tests:

const
const a = "asdfasdfasdfadsfasdfadsfadsfadsfdasfadsf";
let
let a = "asdfasdfasdfadsfasdfadsfadsfadsfdasfadsf";
var
var a = "asdfasdfasdfadsfasdfadsfadsfadsfdasfadsf";

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
const
let
var

Fastest: N/A

Slowest: N/A

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/116.0.0.0 Safari/537.36 Edg/116.0.1938.43

Browser/OS: Chrome 116 on Windows

View result in a separate tab

Test name	Executions per second
const	1044421760.0 Ops/sec
let	1047378432.0 Ops/sec
var	1047488064.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its components.

**What is tested on the provided JSON?**

The JSON represents a JavaScript microbenchmark that tests the speed of assignment for three different variable declarations: `const`, `let`, and `var`. The benchmark measures how long it takes to assign a string value to each variable.

**Options compared**

The benchmark compares the performance of three options:

1. **`const`**: A constant variable declaration, which means the variable's value cannot be changed after it is assigned.
2. **`let`**: A block-scope variable declaration, which allows the variable's value to change within the scope where it is declared.
3. **`var`**: A function-scoped variable declaration, which also allows the variable's value to change within its scope.

**Pros and Cons of each approach**

Here are some pros and cons for each option:

* **`const`**:
	+ Pros: Encourages code to be more predictable and less prone to accidental changes.
	+ Cons: Can lead to "stale" variables if the value is not updated, but this can often be mitigated with other techniques (e.g., using `let` or `const` for smaller values).
* **`let`**:
	+ Pros: Allows for more flexibility in variable assignment and scoping.
	+ Cons: Can lead to code that is less predictable and harder to reason about, especially if not used carefully.
* **`var`**:
	+ Pros: Still widely supported and compatible with older browsers.
	+ Cons: Encourages global scope and can lead to confusing variable names and behavior.

**Library and its purpose**

In this benchmark, no specific library is used. The test cases are simple JavaScript expressions that only use built-in functions and variables.

**Special JS feature or syntax**

This benchmark does not use any special JavaScript features or syntax beyond the three variable declarations being compared. It simply tests the speed of assignment for each option.

**Alternative approaches**

If you're interested in exploring alternative approaches, here are a few examples:

* **Other constant declaration methods**: You could also test `const` using other techniques, such as:
	+ `const x = 0; x += 1;`
	+ `const [x] = [0]; x += 1;`
* **Non-assignment use cases**: You could also test the performance of each option in non-assignment contexts, such as:
	+ `const x = "hello";` vs. `let y = "hello";` vs. `var z = "hello";` (evaluating expressions)
	+ `const x = 0;` vs. `let y = 0;` vs. `var z = 0;` (assigning values to variables in loops)

Keep in mind that these alternative approaches may require additional setup and modifications to the benchmark, but they can provide valuable insights into different aspects of JavaScript performance.

I hope this explanation helps!

Related benchmarks:

const vs let vs var assignment (version: 0)

Assignment speed test

Comparing performance of: const vs let vs var

Created: 2 years ago by: Guest

Jump to the latest result

const

let

var

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):