Benchmark: Test for - MeasureThat.net

Script Preparation code:

var arr = [];
  for (var i = 0; i < 1000; i++) {
    arr[i] = i;
  }

  function someFn(ix) {
    return ix * 5;
  }

Tests:

while
var l = arr.length; while(l--) { someFn(arr[l]); }
for
for (var i = 0; i < arr.length; i++) { someFn(arr[i]); }
for 2
var l = arr.length; for (var i = 0; i < l; i++) { someFn(arr[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
while
for
for 2

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

I'd be happy to explain what's tested in this benchmark.

**Benchmark Purpose**

The benchmark measures the performance of three different approaches for iterating over an array: `while`, `for` (using `arr.length` as the loop condition), and `for 2` (similar to `for`, but using a variable `l` that is initialized with `arr.length`).

**Options Compared**

The benchmark compares the execution speed of these three approaches on a hypothetical JavaScript engine. The options being compared are:

1. **while**: uses a `while` loop with a decrementing counter.
2. **for**: uses a traditional `for` loop with `arr.length` as the loop condition.
3. **for 2**: uses a variation of the traditional `for` loop where the loop condition is stored in a variable `l`, initialized with `arr.length`.

**Pros and Cons**

Here's a brief summary of each approach:

*   **while**: This approach can be more flexible, as it allows for arbitrary termination conditions. However, it requires manual management of the loop counter, which can lead to errors if not implemented correctly.
*   **for**: Traditional `for` loops are generally efficient and easy to read. They are also less prone to errors compared to `while` loops. However, using `arr.length` as the loop condition can be slow due to its potential overhead in calculating the array length at each iteration.
*   **for 2**: This approach combines the benefits of traditional `for` loops with the flexibility of a variable loop counter. It avoids the overhead of recalculating `arr.length` at each iteration, making it potentially faster than the other two approaches.

**Library and Special JS Features**

There are no libraries mentioned in this benchmark definition or test cases. However, JavaScript engines often use various techniques to optimize performance, such as just-in-time (JIT) compilation, caching, and loop unrolling.

**Special JS Feature: Spread Syntax**

Although not explicitly mentioned, the spread syntax (`...`) is used implicitly in the `someFn` function call within each benchmark definition. This feature was introduced in ECMAScript 2015 (ES6) and allows for concise array creation using the spread operator (`...arr`). The use of this syntax does not affect the overall performance comparison but highlights the evolving nature of JavaScript.

**Other Alternatives**

For iterating over arrays, other approaches that are not being tested here include:

*   **forEach**: This method is built into the Array prototype and can be used to iterate over an array without a loop.
*   **reduce**: Another Array prototype method that allows for reducing an array to a single value or performing some operation on each element.
*   **map**: Similar to `forEach`, but returns a new array with transformed values.

In general, the choice of iteration approach depends on the specific use case and performance requirements. While traditional loops are often sufficient, newer features like `forEach` and methods like `reduce` can simplify code and improve readability.

Benchmarking microbenchmarks like this one helps identify optimal approaches for specific tasks in JavaScript, which is essential for optimizing application performance and developing efficient software.

Latest run results:

Run details: (Test run date: 7 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Browser/OS: Chrome 56 on Mac OS X 10.12.1

View result in a separate tab

Test name	Executions per second
while	7156.2 Ops/sec
for	4788.5 Ops/sec
for 2	7145.5 Ops/sec

Related benchmarks:

Test for (version: 0)

Comparing performance of: while vs for vs for 2

Created: 7 years ago by: Guest

Jump to the latest result

while

for

for 2

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):