Benchmark: let vs array 2 - MeasureThat.net

Tests:

arr
let b = []; function a(){ for(let i = 0; i < 10000; i++){ b = [i]; } }
let
function a(){ for(let i = 0; i < 10000; i++){ let c = i; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arr
let

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/126.0.0.0 Safari/537.36

Browser/OS: Chrome 126 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
arr	80377056.0 Ops/sec
let	79942128.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The benchmark you provided measures the performance difference between using `let` and an array (`[]`) to create local variables in a JavaScript function. The test case consists of two individual tests: "arr" (using an array) and "let" (using the `let` keyword).

**Options Compared**

In this benchmark, two options are compared:

1. **Using an Array**: In the "arr" test case, an empty array (`[]`) is used to create a local variable `b`. The array is reassigned on each iteration of the loop.
2. **Using the `let` Keyword**: In the "let" test case, the `let` keyword is used to declare a local variable `c`.

**Pros and Cons**

1. **Using an Array**:
	* Pros: Arrays can be reused in various ways within the scope of the function, making them more flexible.
	* Cons: Reassigning an array on each iteration can lead to performance overhead due to the need for garbage collection.
2. **Using the `let` Keyword**:
	* Pros: `let` is a block-scoped variable declaration, which means it's redeclared on each execution of the function, making it more suitable for loops where the variable needs to be recreated on each iteration.
	* Cons: Redeclaring a variable can lead to slower performance due to the overhead of variable creation and garbage collection.

**Library and Special JavaScript Features**

Neither of these test cases uses any external libraries or special JavaScript features. The code is straightforward and focuses solely on comparing the two variables declaration options.

**Other Considerations**

When benchmarking JavaScript performance, it's essential to consider factors such as:

* Scope: How do different scoping rules (e.g., block scope vs. function scope) affect variable declarations?
* Reassignment: How does reassigning a variable (either an array or a `let` variable) impact performance?
* Garbage Collection: How do garbage collection cycles impact performance in loops where variables are reassigned?

**Alternatives**

If you're interested in exploring similar benchmarks, MeasureThat.net offers many other tests and comparisons. Some examples include:

* Testing the performance of different variable declaration options (e.g., `const`, `var`, etc.)
* Comparing the performance of different data structures (e.g., arrays, objects, sets)
* Benchmarking the performance of different JavaScript engines or versions

Keep in mind that benchmarking is a complex topic, and results may vary depending on the specific use case and environment.

Related benchmarks:

let vs array 2 (version: 0)

is let busted?

Comparing performance of: arr vs let

Created: one year ago by: Guest

Jump to the latest result

arr

let

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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