Benchmark: Test length assign

Script Preparation code:

var obj = Array.from({ length: 10000 }).map((value, i) => i).reduce((val, v) => { val[v] = v; return val; }, {})

Tests:

no var
const entries = Object.values(obj); for (let i = 0; i < entries.length; i++) { const v = entries[i]; }
use var
const entries = Object.values(obj); const len = entries.length; for (let i = 0; i < len; i++) { const v = entries[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
no var
use var

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:106.0) Gecko/20100101 Firefox/106.0

Browser/OS: Firefox 106 on Windows

View result in a separate tab

Test name	Executions per second
no var	4794.4 Ops/sec
use var	4871.6 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 results.

**Benchmark Definition**

The benchmark measures how fast two different approaches are to iterate over an object in JavaScript:

1. **"Use var"**: This approach uses the `var` keyword to declare variables within the scope of the loop.
2. **"No var"**: This approach does not use the `var` keyword, instead using the `const` keyword for constant variables or relying on the `let` keyword for declared but reassignable variables.

**Options Compared**

The benchmark compares the performance of these two approaches in terms of:

* Speed (measured by "ExecutionsPerSecond")
* Use of `var`, `const`, and `let`

**Pros and Cons**

### "Use var"

Pros:

* Can be more efficient in certain cases, as it allows for faster scope resolution
* Easier to write and understand for beginners

Cons:

* Can lead to hoisting issues if not used carefully (e.g., using `var` inside a loop that's not immediately followed by the loop declaration)
* May cause more confusion due to its older syntax

### "No var"

Pros:

* More modern and explicit syntax
* Avoids hoisting issues
* Generally considered better practice for new code

Cons:

* Can lead to slightly slower performance in some cases (depending on the specific use case)

**Library**

None are used in this benchmark. However, if you notice any libraries being used elsewhere in your benchmarking efforts, please let me know and I'd be happy to help.

**Special JS Features or Syntax**

This benchmark uses:

* `let` for declared but reassignable variables (not explicitly mentioned in the benchmark definition, but implied by not using `var`)
* `const` for constant variables (used in "No var" approach)
* Arrow functions (`=>`) and template literals (`\r\n`) for concise code snippets

**Other Considerations**

This benchmark seems to be primarily focused on measuring performance differences between these two approaches. However, keep in mind that there might be other factors at play, such as:

* The size of the object being iterated over (the `Array.from` approach creates an array with 10,000 elements)
* The specifics of the JavaScript engine or browser being used
* Potential side effects or memory allocations during execution

**Alternatives**

If you want to extend this benchmark or explore other variations:

* Measure performance differences for other JavaScript features, such as:
	+ Block scope and closure mechanics (e.g., `let` vs. `var` with different scopes)
	+ Object property access patterns
	+ Method calls vs. property accesses on objects
* Compare performance across different browsers or JavaScript engines
* Consider adding more object sizes or complexity to the iteration process

Related benchmarks:

Test length assign (version: 0)

Comparing performance of: no var vs use var

Created: 2 years ago by: Guest

Jump to the latest result

no var

use 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):