Benchmark: last i in Array - MeasureThat.net

Script Preparation code:

var myArr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Tests:

i less myArr.Length
for(var i = 0 ; i < myArr.Length ; ++i ){ myArr[i]+1 }
myArr[i]
for(var i = 0 ; myArr[i] ; ++i ){ myArr[i]+1 }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
i less myArr.Length
myArr[i]

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/109.0.0.0 Safari/537.36

Browser/OS: Chrome 109 on Windows

View result in a separate tab

i less myArr.Length

13.4M/s

myArr[i]

639K/s

View exact numbers

Test name	Executions per second
✓ i less myArr.Length	13,436,562 Ops/sec
myArr[i]	639,199 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested.

**Benchmark Definition**

The benchmark is defined by two script preparation codes, which are:

1. `var myArr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];`
This code creates an array `myArr` with 10 elements.

2. Two HTML preparation codes are not provided, but they are likely used to set up the testing environment.

**Individual Test Cases**

There are two test cases:

1. `for(var i = 0 ; i < myArr.Length ; ++i ){\r\n  myArr[i]+1\r\n}`
This code uses the `Length` property of the array to get its length and then iterates over it using a traditional for loop.

2. `for(var i = 0 ; myArr[i] ; ++i ){\r\n  myArr[i]+1\r\n}`
This code directly accesses the elements of the array using the index `i` in the condition of the for loop, which is known as "incremental indexing". This approach avoids checking if the element exists or not.

**Comparison**

The two approaches are compared:

* The first test case uses the traditional way to access array indices (`myArr[i]`) and increments a separate variable (`i`) using the `Length` property. This approach is straightforward but may be slower due to the overhead of accessing the `Length` property.
* The second test case uses incremental indexing, where the condition of the for loop directly accesses the elements of the array using `myArr[i]`. This approach can be faster because it avoids checking if the element exists.

**Pros and Cons**

Pros:

* Incremental indexing (second test case) can be faster because it avoids checking if the element exists.
* Traditional access (`myArr[i]`) is more straightforward and easier to understand for some developers.

Cons:

* Incremental indexing may not work as expected in certain situations, such as when the array is empty or contains null values.
* The use of `Length` property can add overhead due to its computational cost.

**Library Usage**

None of the benchmark cases explicitly uses any libraries. However, it's worth noting that some JavaScript engines and browsers have built-in optimizations for array iteration, which might affect the results.

**Special JS Features or Syntax**

There are no special features or syntax used in these test cases. They use standard JavaScript features such as arrays, for loops, and incrementing variables.

**Other Alternatives**

If you wanted to create a similar benchmark, you could consider adding more test cases that compare different indexing approaches, array iteration methods (e.g., `forEach`, `map`, or `reduce`), or other operations on the array. You could also explore using modern JavaScript features like `let` and `const` instead of traditional `var`.

Keep in mind that measuring performance in JavaScript can be complex due to factors like engine optimizations, caching, and variable scoping. When creating benchmarks, it's essential to ensure that the test cases are representative of real-world scenarios and that the measurements are accurate.

last i in Array (version: 0)

myArr.Length vs myArr[i]

Comparing performance of: `i less myArr.Length vs myArr[i]`

Created: one year ago by: Guest

Go to the latest result

i less myArr.Length

myArr[i]

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

last i in Array (version: 0)

myArr.Length vs myArr[i]

Comparing performance of: i less myArr.Length vs myArr[i]

Created: one year ago by: Guest

Go to the latest result

i less myArr.Length

myArr[i]

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `i less myArr.Length vs myArr[i]`