Benchmark: loops_and_stuff - MeasureThat.net

Script Preparation code:

var arr = [1, 2, 4 , 5, 66, 38, 39, 3993, 33, "test", "hello", 93, 93, 20, 77, "hu", 92, 18, 4 , 5, 66, 38, 39, 3993, 33, "test", "hello", 93, 93, 20, 77, "hu", 92, 18, 4 , 5, 66, 38, 39, 3993, 33, "test", "hello", 93, 93, 20, 77, "hu", 92, 18, 4 , 5, 66, 38, 39, 3993, 33, "test", "hello", 93, 93, 20, 77, "hu", 92, 18, 4 , 5, 66, 38, 39, 3993, 33, "test", "hello", 93, 93, 20, 77, "hu", 92, 18, 4 , 5, 66, 38, 39, 3993, 33, "test", "hello", 93, 93, 20, 77, "hu", 92, 18];
var tmp;

Tests:

while loop
var len = arr.length; while(len--) { tmp = arr[len]; }
uncached length
for (let i = 0; i < arr.length; i++) { tmp = arr[i]; }
cached length postfix
for (let i = 0, len = arr.length; i < len; i++) { tmp = arr[i]; }
cached length prefix
for (let i = 0, len = arr.length; i < len; ++i) { tmp = arr[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
while loop
uncached length
cached length postfix
cached length prefix

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Overview**

The provided benchmark measures the performance of different loop constructs in JavaScript: while loops, uncached length for loops, cached length prefix for loops, and cached length postfix for loops. The benchmark script generates an array `arr` with 40 elements and uses it to iterate through the array using each of these loop constructs.

**Loop Constructs**

1. **While Loop**: This loop construct uses a while loop that decrements the index `len` until it reaches 0, accessing the element at the current index in the array.
```javascript
while(len--) {
    tmp = arr[len];
}
```
Pros: Simple to implement and works well for small arrays.

Cons: Since the length of the array is not cached, it requires a constant number of operations to retrieve the length. This can lead to slower performance for large arrays.

2. **Uncached Length For Loop**: This loop construct uses a traditional for loop that accesses the length of the array using `arr.length` and then decrements the index.
```javascript
for (let i = 0; i < arr.length; i++) {
    tmp = arr[i];
}
```
Pros: This approach is similar to the while loop, but with the added benefit of being a traditional for loop.

Cons: Since the length of the array is not cached, it requires a constant number of operations to retrieve the length. This can lead to slower performance for large arrays.

3. **Cached Length Prefix For Loop**: This loop construct uses a for loop that accesses the length of the array using `len = arr.length` and then decrements the index.
```javascript
for (let i = 0, len = arr.length; i < len; i++) {
    tmp = arr[i];
}
```
Pros: By caching the length in a variable, this approach reduces the number of operations required to access the array.

Cons: The prefix notation can be less readable than the postfix notation.

4. **Cached Length Postfix For Loop**: This loop construct uses a for loop that accesses the length of the array using `len = arr.length` and then decrements the index in a postfix notation.
```javascript
for (let i = 0, len = arr.length; i < len; ++i) {
    tmp = arr[i];
}
```
Pros: By caching the length in a variable and using a postfix notation, this approach is similar to the cached length prefix for loop but with less readability.

Cons: The postfix notation can be less readable than the prefix notation.

**Library Used**

None of the provided benchmark definitions use any external libraries. However, the script uses a temporary variable `tmp` to store the array elements during iteration.

**Special JS Features or Syntax**

The benchmark defines four different loop constructs, but none of them require special JavaScript features or syntax beyond the standard language features available in modern browsers.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.92 Safari/537.36

Browser/OS: Chrome 69 on Mac OS X 10.13.6

View result in a separate tab

Test name	Executions per second
while loop	59598.0 Ops/sec
uncached length	43028.9 Ops/sec
cached length postfix	59822.3 Ops/sec
cached length prefix	60395.6 Ops/sec

Related benchmarks:

loops_and_stuff (version: 0)

Comparing performance of: while loop vs uncached length vs cached length postfix vs cached length prefix

Created: 6 years ago by: Guest

Jump to the latest result

while loop

uncached length

cached length postfix

cached length prefix

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):