Benchmark: Nodelist iterator

Script Preparation code:

for(i=0; i<100; i++){
  let elem = document.createElement('div');
  elem.id = i;
  document.body.append(elem);
}

Tests:

Spread
const elements = document.querySelectorAll('div'); [...elements].map(e => e.id);
Array.from
const elements = document.querySelectorAll('div'); Array.from(elements, e => e.id);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Array.from

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested, compared, and considered.

**Benchmark Definition**

The benchmark definition is a JavaScript code snippet that creates an array of HTML elements using `document.createElement` and appends them to the DOM. This setup is repeated 100 times in a loop. The purpose of this test case is to measure the performance of iterating over an array of elements, likely to compare different methods for extracting values from the elements.

**Options Compared**

Two options are compared:

1. **Spread Syntax (`[...elements].map(e => e.id);`)**
2. **Array.from Method (`Array.from(elements, e => e.id);`)**

These two approaches have different pros and cons:

* **Spread Syntax:**
	+ Pros:
		- More concise and readable.
		- Can be more efficient since it doesn't require creating an intermediate array.
	+ Cons:
		- May not work as expected in older browsers that don't support this syntax (e.g., IE).
		- Can lead to issues with memory management if the spread operator is used extensively.
* **Array.from Method:**
	+ Pros:
		- More robust and widely supported across different browsers.
		- Allows for more fine-grained control over iteration.
	+ Cons:
		- Requires creating an intermediate array, which may impact performance.

**Library Used**

There is no library explicitly used in the provided benchmark definition. However, `document.querySelectorAll` and `Array.from` are built-in JavaScript methods that work across different browsers.

**Special JS Feature or Syntax**

The spread syntax (`[...elements].map(e => e.id);`) uses a modern JavaScript feature called **rest operator spread** (also known as the **spread operator**) (`[...array]`). This is a relatively new feature introduced in ECMAScript 2018. Older browsers may not support this syntax.

**Other Considerations**

When designing benchmarks, it's essential to consider factors like:

* **Benchmarking tools**: Measure performance using a reliable benchmarking tool, such as `benchmark.js` or `jsbench`.
* **Code execution**: Optimize code execution by avoiding unnecessary computations and ensuring that all test cases execute consistently.
* **Platform support**: Test on multiple platforms and browsers to ensure that the results are representative of real-world usage.
* **Noise reduction**: Minimize noise (e.g., random fluctuations) in benchmarking data by using techniques like averaging or smoothing.

**Alternatives**

Other alternatives for measuring performance differences in JavaScript could include:

1. **Benchmarking libraries**: `benchmark.js`, `jsbench`, or `fast-benchmark`.
2. **Simplified benchmarks**: Focusing on specific, simplified code snippets that isolate the performance difference being measured.
3. **Performance profiling tools**: Using built-in browser developer tools (e.g., Chrome DevTools) or third-party tools like `perfkit` to analyze performance.

By considering these factors and alternatives, developers can create more accurate and reliable benchmarks for measuring JavaScript performance differences.

Related benchmarks:

Nodelist iterator (version: 0)

Comparing performance of: Spread vs Array.from

Created: 5 years ago by: Guest

Jump to the latest result

Spread

Array.from

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):