Benchmark: Looping over Arrays

Script Preparation code:

arr = Array(10000).fill().map(x=>Math.random())

Tests:

.map
arr.map(x=>{});
.forEach
arr.forEach(x=>{});
for loop
for(let i = 0;i<arr.length;i++){let x=arr[i]}
for of loop
for(let x of arr){}
for of keys
for(let i of arr.keys()){let x = arr[i]}

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.map
.forEach
for loop
for of loop
for of keys

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The provided JSON represents a benchmark definition for measuring the performance of different looping constructs in JavaScript. The script preparation code creates an array of 10,000 random numbers using the `Array.prototype.fill()` and `Array.prototype.map()` methods. This ensures that all tests have the same input data, allowing for fair comparisons.

**Options Compared**

The benchmark compares four different looping constructs:

1. **For Loop**: A traditional, manual loop using a `for` statement.
2. **For Of Loop**: A newer looping construct introduced in ECMAScript 2015 (ES6), which allows iterating over arrays without explicit indexing.
3. **forEach Method**: The `Array.prototype.forEach()` method, which calls a provided callback function for each element in the array.
4. **Map Method**: The `Array.prototype.map()` method, which returns a new array with the results of applying a provided transformation function to each element in the original array.

**Pros and Cons**

Here's a brief summary of the pros and cons of each looping construct:

* **For Loop**:
	+ Pros: Wide browser support, easy to understand for beginners.
	+ Cons: Can be verbose, error-prone due to manual indexing.
* **For Of Loop**:
	+ Pros: Concise syntax, fewer errors due to implicit indexing.
	+ Cons: Introduced in ES6, may require additional setup or polyfills for older browsers.
* **forEach Method**:
	+ Pros: Easy to use, less prone to errors than manual loops.
	+ Cons: May not be as efficient as native looping constructs, can have performance overhead due to callback function execution.
* **Map Method**:
	+ Pros: Concise syntax, easy to chain multiple transformations together.
	+ Cons: Returns a new array, which may incur additional memory allocation and copying.

**Other Considerations**

When evaluating the performance of these looping constructs, it's essential to consider factors like:

* Cache locality: How well do the loops access elements in contiguous memory locations?
* Branch prediction: Can the compiler or runtime predict the execution branch of the loop?

**Libraries and Special Features**

No libraries are used in this benchmark. However, if a test case uses an external library, it's essential to consider the performance impact of that library on the overall benchmark result.

If a test case includes special JavaScript features like `async/await`, `promises`, or `genurescript`, these should be carefully evaluated and potentially excluded from the benchmark results to ensure fairness and relevance.

**Alternatives**

For those interested in exploring alternative looping constructs, some notable options include:

* **Native Web Workers**: Can utilize parallel processing for tasks that would otherwise block the main thread.
* **Native Web Threads**: A new API for running tasks concurrently with the main thread, suitable for CPU-bound computations.
* **Third-party libraries like Looper.js** or **ArrayLoop**: Specialized libraries optimized for different looping constructs, which may offer performance benefits over native implementations.

Keep in mind that these alternatives might introduce additional dependencies, overhead, or complexity to your benchmarking setup.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36

Browser/OS: Chrome 79 on Windows

View result in a separate tab

Test name	Executions per second
.map	1228.9 Ops/sec
.forEach	1508.7 Ops/sec
for loop	89.7 Ops/sec
for of loop	10460.1 Ops/sec
for of keys	175.5 Ops/sec

Related benchmarks:

Looping over Arrays (version: 0)

Comparing performance of: .map vs .forEach vs for loop vs for of loop vs for of keys

Created: 4 years ago by: Guest

Jump to the latest result

.map

.forEach

for loop

for of loop

for of keys

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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