Benchmark: saving indexOf result in a const and referencing it as a var is faster or no?

Script Preparation code:

var array = []

for (let i = 0; i < 100; i++) {
  array.push(i)
}

Tests:

Memorizing
const getRuleIndex = (number, arr) => { const indexOf = arr.indexOf(number) if (indexOf >= 0) { return indexOf } } getRuleIndex(50, array)
Doing it again
const getRuleIndex = (number, arr) => { if (arr.indexOf(number) >= 0) { return arr.indexOf(number) } } getRuleIndex(50, array)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Memorizing
Doing it again

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark JSON and explain what's being tested, compared, and the pros/cons of each approach.

**Benchmark Definition**

The first benchmark measures whether saving the result of `indexOf` in a constant (`const`) is faster than referencing it as a variable (`var`). The script preparation code creates an array with 100 elements, which will be used to test the performance difference between these two approaches.

**Script Preparation Code**
```javascript
var array = [];
for (let i = 0; i < 100; i++) {
  array.push(i);
}
```
This code creates an empty array and populates it with 100 elements using a `for` loop. The resulting array is stored in the `array` variable.

**Html Preparation Code**
Since there's no HTML preparation code, we can assume that this benchmark only focuses on the JavaScript performance aspect.

**Individual Test Cases**

There are two test cases:

1. **"Memorizing"**: This test case uses a constant (`const`) to store the result of `indexOf`, like so:
```javascript
const getRuleIndex = (number, arr) => {
  const indexOf = arr.indexOf(number);
  if (indexOf >= 0) {
    return indexOf;
  }
}
getRuleIndex(50, array);
```
In this test case, we first calculate the result of `indexOf` using a constant (`const`) and then assign it to the local variable `indexOf`. We store this value in a constant (`const`) before returning it.

2. **"Doing it again"**: This test case uses a variable (`var`) to store the result of `indexOf`, like so:
```javascript
if (arr.indexOf(number) >= 0) {
  return arr.indexOf(number);
}
getRuleIndex(50, array);
```
In this test case, we calculate the result of `indexOf` directly using a `var` and then assign it to the local variable. We don't store this value in any constant or variable before returning it.

**Pros and Cons**

**Constant approach (Memorizing)**

* Pros:
	+ The compiler can optimize the code better, since the result is stored in a constant.
	+ It's more predictable and efficient for the JavaScript engine to calculate the result once and store it in a constant.
* Cons:
	+ In some cases, the compiler might not be able to optimize this approach as well as the variable approach.

**Variable approach (Doing it again)**

* Pros:
	+ The compiler can't optimize the code as much, since the result is used directly and not stored in a variable.
	+ It's more flexible and allows for potential future optimizations by the JavaScript engine.
* Cons:
	+ The JavaScript engine has to calculate the result of `indexOf` twice, which can lead to slower performance.

**Library Used**

There is no explicit library mentioned in the provided JSON. However, it's worth noting that the `array` variable used in both test cases is a built-in JavaScript array.

**Special JS Feature or Syntax**

Neither of these two approaches uses any special JavaScript features or syntax beyond what's considered standard in modern JavaScript.

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/117.0.0.0 Safari/537.36

Browser/OS: Chrome 117 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Memorizing	28825096.0 Ops/sec
Doing it again	28680304.0 Ops/sec

Related benchmarks:

saving indexOf result in a const and referencing it as a var is faster or no? (version: 0)

Comparing performance of: Memorizing vs Doing it again

Created: one year ago by: Guest

Jump to the latest result

Memorizing

Doing it again

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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