Benchmark: Test length assign 100k

Script Preparation code:

var obj = Array.from({ length: 100000 }).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

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and individual test cases to understand what's being tested.

**Benchmark Definition**

The benchmark is designed to measure the performance of two approaches for iterating over an object in JavaScript:

1. Using `Object.values()` with a simple `for` loop
2. Using `Object.values()` followed by assigning the length of the resulting array to a variable and then using that variable in a `for` loop

The script preparation code creates a large object (`obj`) with 100,000 properties, where each property is assigned a value equal to its index.

**Options Compared**

Two options are being compared:

1. **No `var`**: This approach uses the `Object.values()` method directly in the `for` loop. The length of the resulting array is not stored in a variable.
2. **Use `var`**: In this approach, the length of the resulting array is assigned to a variable (`len`) and then used in the `for` loop.

**Pros and Cons**

**No `var`**

Pros:

* Simplified code
* Less chance of introducing errors due to variable scope

Cons:

* Might lead to slower performance if the compiler or interpreter needs to perform more calculations during the execution of the loop

**Use `var`**

Pros:

* Can potentially lead to better performance, as some compilers/interpreters might optimize the loop with the stored length value
* Allows for easier debugging and understanding of the loop behavior

Cons:

* Introduces an additional variable that needs to be managed
* Might increase the chance of introducing errors due to variable scope issues

**Other Considerations**

In both approaches, using `Object.values()` is optimized by the JavaScript engine, which avoids the need for additional iterations to access the object's properties. However, this optimization might not always result in performance differences.

Additionally, it's worth noting that the test case assumes a specific version of Chrome (107) and its corresponding platform (Desktop on Windows). If the benchmark were to be run on different platforms or browsers, the results might vary.

**Library/Functionality Used**

None. The benchmark only relies on built-in JavaScript features, such as `Array.from()`, `map()`, `reduce()`, and `Object.values()`.

**Special JS Feature/Syntax (Not applicable)**

No special JavaScript features or syntax are used in this benchmark.

Now, let's take a look at the individual test cases:

**Test Case 1: "no var"**

This test case runs the `for` loop directly using the result of `Object.values()`, without assigning the length to a variable. The benchmark measures the execution frequency (ExecutionsPerSecond) for this approach.

**Test Case 2: "use var"**

In this test case, the length of the resulting array is assigned to a variable (`len`) and then used in the `for` loop. Again, the benchmark measures the execution frequency for this approach.

Both test cases are designed to compare the performance of iterating over an object using `Object.values()`, with and without assigning the length to a variable. The results from these two test cases will help determine which approach is faster.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Browser/OS: Chrome 107 on Windows

View result in a separate tab

Test name	Executions per second
no var	2735.5 Ops/sec
use var	2498.8 Ops/sec

Related benchmarks:

Test length assign 100k (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 26 days ago):