Benchmark: let & var change

Tests:

let
let foo = "foo" foo = "bar"
var
var foo = "foo" foo = "bar"

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
let
var

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its test cases.

**What is being tested?**

The benchmark measures the performance difference between using `let` and `var` keywords in JavaScript. Both `let` and `var` are used for declaring variables, but they have different scoping behaviors. `let` has block scope, meaning it only applies within the block it's declared inside, while `var` has function scope, applying to the entire surrounding function.

**Options compared**

The two options being compared are:

1. **`let foo = "foo" \n foo = "bar"`**: This is a variable assignment using `let`, where a new value is assigned to an existing variable.
2. **`var foo = "foo" \n foo = "bar"`**: This is a variable assignment using `var`, also assigning a new value to an existing variable.

**Pros and Cons**

* **`let`**:
	+ Pros: Block scope, which can help avoid global variables and reduce polluting the global namespace. Also, it's more modern and commonly used in newer JavaScript versions.
	+ Cons: Can't be reassigned with a new value outside its block scope (unless you use `const let` or `let const` for immutable blocks).
* **`var`**:
	+ Pros: Can be redeclared with the same name within the same scope, and it's supported by older JavaScript versions.
	+ Cons: Function scope, which can lead to unexpected variable behaviors in large codebases. Also, it's generally considered less modern and more polluting than `let`.

**Library usage**

There is no explicit library mentioned in the benchmark definition or test cases. However, the browser specified (`Chrome 67`) might be using its own libraries or extensions that are not explicitly declared.

**Special JS features or syntax**

The benchmark does not explicitly mention any special JavaScript features or syntax being used. The variable assignments and reassignments described are basic and standard JavaScript constructs.

**Other alternatives**

If you wanted to measure the performance of other JavaScript variables, such as `const`, `function`, or `let const`, you could add additional test cases with different assignments and reassignments.

To give a more comprehensive understanding, here's an updated benchmark definition with additional test cases:

```json
{
    "Name": "JavaScript Variable Performance",
    "Description": null,
    "Script Preparation Code": null,
    "Html Preparation Code": null
}
[
    {
        "Benchmark Definition": "let foo = \"foo\"\r\nfoo = \"bar\"",
        "Test Name": "let "
    },
    {
        "Benchmark Definition": "var foo = \"foo\"\r\nfoo = \"bar\"",
        "Test Name": "var"
    },
    {
        "Benchmark Definition": "const foo = \"foo\"\r\nfoo = \"bar\"",
        "Test Name": "const"
    },
    {
        "Benchmark Definition": "function foo() { foo() }",
        "Test Name": "function"
    }
]
```

This updated benchmark would measure the performance of `let`, `var`, `const`, and `function` variables in different scenarios.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.79 Safari/537.36

Browser/OS: Chrome 67 on Mac OS X 10.13.5

View result in a separate tab

Test name	Executions per second
let	941462016.0 Ops/sec
var	942945472.0 Ops/sec

Related benchmarks:

let & var change (version: 0)

Comparing performance of: let vs var

Created: 6 years ago by: Guest

Jump to the latest result

let

var

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):