Benchmark: cached for loop vs for each

Script Preparation code:

var arr = [];
var count = 1000;
for(var i = 0; i<count; i++)
{
  arr.push(i);
}

Tests:

cached for loop
var arrLen = arr.length; var sum = 0; for (var i = 0; i < arrLen; i++){ sum = arr[i]; }
foreach loop
var sum = 0; arr.forEach(elem => { sum = elem; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
cached for loop
foreach loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided JSON data and explain what's being tested in this JavaScript microbenchmark.

**Benchmark Definition**

The benchmark is defined as a comparison between two approaches: using a cached `for` loop versus using a `forEach` loop to iterate over an array. The goal is to determine which approach is faster.

**Options Compared**

Two options are compared:

1. **Cached `for` loop**: This approach uses a traditional `for` loop with the array length stored in a variable (`arrLen`) and iterates over the array using the index (`i`). This allows for some caching, as the value of `arrLen` is only calculated once.
2. **`forEach` loop**: This approach uses the `forEach` method provided by modern JavaScript engines to iterate over the array. The callback function takes an element from the array as its argument.

**Pros and Cons**

**Cached `for` Loop:**

Pros:

* Can be more efficient, as it avoids the overhead of a function call for each iteration.
* Allows for caching of the loop counter value.

Cons:

* Requires manual management of the index variable (`i`) and loop counter (`arrLen`).
* May not work correctly if the array is modified during iteration.

**`forEach` Loop:**

Pros:

* Is more concise and easier to read, as it eliminates the need for a traditional `for` loop.
* Does not require manual management of the index variable or loop counter.

Cons:

* Can be slower due to the overhead of the function call for each iteration.
* May not work correctly if the array is modified during iteration.

**Library and Syntax**

No libraries are used in this benchmark. The focus is on comparing two basic JavaScript iteration patterns.

**Special JS Feature/Syntax (None)**

There are no special JavaScript features or syntax used in this benchmark.

**Other Alternatives**

Other alternatives for iterating over arrays could include:

* Using a `for...of` loop, which provides an even more concise and readable way to iterate over arrays.
* Using the `map()` method, which applies a function to each element of an array and returns a new array with the results.
* Using the `reduce()` method, which applies a function to each element of an array and reduces it to a single value.

These alternatives may not be suitable for every use case, but they demonstrate the flexibility of JavaScript's iteration methods.

Related benchmarks:

cached for loop vs for each (version: 0)

Comparing performance of: cached for loop vs foreach loop

Created: 3 years ago by: Guest

Jump to the latest result

cached for loop

foreach loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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