Benchmark: loop speed - MeasureThat.net

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

var i1 = 0;
var i2 = 0;
var arr = [1,2,3,4,5,6,7,8,9]

Tests:

arr[i]
i2 = 0; for( ; arr[i2] ; i2++ ){ arr + 1 ; };
i1<arr.length
i1 = 0; for( ; i1<arr.length ; i1++ ){ arr + 1 ; };

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Chrome 5 runs

i1<arr.length

162K/s

arr[i]

162K/s

View exact numbers

✓ i1<arr.length: 162,266 ops/sec
• arr[i]: 161,523 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arr[i]
i1<arr.length

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

arr[i]

160K/s

i1<arr.length

160K/s

View exact numbers

Test name	Executions per second
✓ arr[i]	159,738 Ops/sec
i1<arr.length	159,618 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

### Benchmark Overview

The benchmark defined in the provided JSON is focused on measuring the performance of two different approaches for looping through an array in JavaScript. The array being used is a small fixed-size array `[1,2,3,4,5,6,7,8,9]`. The main aim of this benchmark is to evaluate the impact of different conditions in the loop construct on execution speed.

### Test Cases Explained

The benchmark contains two distinct test cases:

1. **Test Case: "arr[i]"**
   - **Code**: 
     ```javascript
     i2 = 0;
     for( ; arr[i2]; i2++){
       arr + 1;
     };
     ```
   - **Description**: In this test case, the loop condition is checking whether `arr[i2]` is truthy. This means that the loop continues as long as `arr[i2]` is not `undefined` or `null`. It inherently relies on array indexing with a trailing condition.

2. **Test Case: "i1<arr.length"**
   - **Code**:
     ```javascript
     i1 = 0;
     for( ; i1 < arr.length; i1++){
       arr + 1;
     };
     ```
   - **Description**: In this test case, the loop condition explicitly compares the index `i1` to `arr.length`. The loop will terminate once `i1` is equal to the length of the array.

### Pros and Cons of Each Approach

**1. "arr[i]" Method**
   - **Pros**:
     - Simplicity in the condition check, as it directly checks the value at each index.
     - Potentially faster for some JavaScript engines with optimizations related to enforcement of truthy values.
   - **Cons**:
     - This method may lead to potential pitfalls if used on an empty array or if the array contains falsy values such as `0` or `null`, which could cause the loop to terminate prematurely and lead to unexpected behavior.
     - Potentially less clarity for developers unfamiliar with this syntax.

**2. "i1<arr.length" Method**
   - **Pros**:
     - More explicit and clear; it clearly indicates the loop is based on the defined length of the array which prevents errors related to content in the array.
     - A more standard and common approach which is more readable and less prone to logical errors.
   - **Cons**:
     - Might be slightly less efficient in scenarios where the loop runs many times and the overhead of fetching the length of the array each time becomes significant; though this is generally negligible for small arrays.
   
### Considerations and Alternatives

In addition to the two tested methods, there are other common patterns for iterating over arrays in JavaScript that could be considered for performance benchmarks:

1. **Using `forEach`**:
   - A method of the Array prototype that executes a provided function once for each array element. While this is more readable, it may introduce overhead due to function calls.
   
2. **Using `for...of`**:
   - A modern loop construct that simplifies iteration over iterable objects, including arrays. This improves readability but has its own performance characteristics that merit testing.

3. **Using `map` or `filter`**:
   - While designed for transforming or filtering arrays instead of pure iteration, these methods can also be used to traverse arrays, but they typically return new arrays and create additional performance overhead due to memory allocation.

### Conclusion

The benchmark aims to provide insights regarding the execution speed differences between two common looping constructs. While the performance between the two is quite close, the choice of method should also take into consideration code clarity, maintainability, and potential error sources. Ultimately, the best choice will often depend on the specific context in which the loop is being used.

loop speed (version: 1)

i < len versus none item

Comparing performance of: `arr[i] vs i1<arr.length`

Created: one year ago by: Guest

Go to the latest result

arr[i]

i1<arr.length

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Chrome 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

loop speed (version: 1)

i < len versus none item

Comparing performance of: arr[i] vs i1<arr.length

Created: one year ago by: Guest

Go to the latest result

arr[i]

i1<arr.length

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Chrome 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

Related benchmarks

Comparing performance of: `arr[i] vs i1<arr.length`