Benchmark: Array fill map, vs while loop

Script Preparation code:

var iterations = 10000;

Tests:

while
var i = 0; while ( i < iterations ) { i++ console.log(i); }
fill and map
Array(iterations).fill('').map((value, index) => index);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
while
fill and map

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/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Windows

View result in a separate tab

Test name	Executions per second
while	15.4 Ops/sec
fill and map	18747.6 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the benchmark and its results.

The provided JSON represents a JavaScript microbenchmark test case for measuring performance differences between two approaches: using an array fill followed by a map method (denoted as "fill and map"), and using a traditional while loop (denoted as "while").

**Options Compared**

In this benchmark, the following options are compared:

1. **Array Fill + Map**: This approach involves creating an empty array with `Array(iterations).fill('')`, followed by mapping over it to log each index.
2. **While Loop**: This approach uses a traditional while loop that increments an index variable (`i`) and logs its value to the console.

**Pros and Cons**

Both approaches have their trade-offs:

1. **Array Fill + Map**:
	* Pros: More concise and readable code, leverages modern JavaScript features.
	* Cons: May incur additional overhead due to creating an array, even if it's empty.
2. **While Loop**:
	* Pros: Lowers memory usage since no extra array is created, avoids potential issues with `Array` constructor caching.
	* Cons: More verbose code and may be less readable.

In general, the while loop approach can provide better performance when memory is a concern or in cases where every millisecond counts. However, in most scenarios, the readability and conciseness of the array fill + map approach outweighs any minor performance differences.

**Library Usage**

There is no explicit library usage mentioned in this benchmark. However, it's worth noting that `Array(iterations).fill('')` uses the modern JavaScript Array constructor with a shorthand syntax, which was introduced in ECMAScript 5 (2011).

**Special JS Features/Syntax**

The test case does not explicitly use any special JavaScript features or syntax beyond what's mentioned earlier.

**Other Considerations**

To further optimize this benchmark, consider using:

*   **Profiling tools**: Utilize built-in profiling tools like Chrome DevTools' Performance tab to identify performance bottlenecks and focus on optimization areas.
*   **Benchmarking frameworks**: Explore specialized benchmarking libraries or frameworks, such as Benchmark.js or JSBench, which can help standardize the test process and provide more accurate results.

**Alternatives**

If you'd like to explore alternative approaches or optimize this specific benchmark further, consider the following:

1.  **Loop unrolling**: Instead of incrementing a single variable (`i`), try using multiple assignments within each iteration (e.g., `i = i + 1; j++;`) to reduce branch prediction overhead.
2.  **Array constructor caching**: Investigate whether the `Array` constructor is being cached in previous iterations, potentially affecting performance. You can check if the browser has implemented array constructor caching using tools like Chrome DevTools' Performance tab.
3.  **Function inlining**: Use a tool like UglifyJS or a similar library to analyze and optimize your JavaScript code for better performance.
4.  **Parallel execution**: Consider running multiple iterations of both approaches concurrently using Web Workers, async/await, or other parallelization techniques to take full advantage of multi-core processors.

Keep in mind that the specific optimizations you choose will depend on the trade-offs between readability, maintainability, and performance optimization goals for your use case.

Related benchmarks:

Array fill map, vs while loop (version: 0)

People tend to use array fil and then foreach, we know foreach is faster than a for loop, but is it also faster if you use array fill first?

Comparing performance of: while vs fill and map

Created: one year ago by: Guest

Jump to the latest result

while

fill and map

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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