Benchmark: 1000 x event listeners vs single event listener with array of 1000 callbacks

Tests:

1000 event listeners
let i = 1001; const results = []; while (--i) { const index = i; window.addEventListener('custom:test', () => { results.push(index); }, {once: true}); } window.dispatchEvent(new CustomEvent('custom:test'));
1 event listener handling an array of 1000 callbacks
let i = 1001; const results = []; const callbacks = []; while (--i) { const index = i; callbacks.push(() => { results.push(index); }) } window.addEventListener('custom:test', () => { callbacks.forEach((cb) => { cb() }) }, {once: true}); window.dispatchEvent(new CustomEvent('custom:test'));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
1000 event listeners
1 event listener handling an array of 1000 callbacks

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:144.0) Gecko/20100101 Firefox/144.0

Browser/OS: Firefox 144 on Mac OS X 10.15

View result in a separate tab

1 event listener handling an array of 1000 callbacks

50K/s

1000 event listeners

410/s

View exact numbers

Test name	Executions per second
✓ 1 event listener handling an array of 1000 callbacks	50,412 Ops/sec
1000 event listeners	410 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided benchmark measures the performance difference between two approaches to handling an array of callbacks in JavaScript:

1. **Individual Event Listeners**: Each callback is added as a separate event listener, with `window.addEventListener` being called 1000 times with different indices.
2. **Single Event Listener with Array of Callbacks**: A single event listener is created and passed an array of callbacks to handle.

**Comparison**

The benchmark compares the performance of these two approaches:

* **Individual Event Listeners**: The test creates 1000 separate event listeners, each bound to a specific callback function.
* **Single Event Listener with Array of Callbacks**: The test creates a single event listener and passes an array of callbacks to it.

**Pros and Cons**

### Individual Event Listeners

Pros:

* Easy to implement and understand
* Allows for fine-grained control over each callback

Cons:

* Creates 1000 separate objects in memory, leading to increased memory usage
* May lead to performance issues due to the overhead of creating and removing event listeners

### Single Event Listener with Array of Callbacks

Pros:

* Reduces memory usage compared to individual event listeners
* Can be more efficient since only one event listener needs to be created and managed

Cons:

* Requires a single function that can handle all callbacks, which may lead to increased complexity
* May not provide the same level of control over each callback as individual event listeners

**Library and Special JS Feature**

The benchmark uses the `CustomEvent` API, which is a standard feature in modern browsers. A `CustomEvent` is an event that is defined by the developer, but is still handled by the browser.

No special JavaScript features or syntax are used in this benchmark.

**Other Alternatives**

Alternative approaches to handling arrays of callbacks might include:

* **Using a callback queue**: Instead of adding all callbacks to an array and passing it to a single function, a callback queue can be implemented to process callbacks one by one.
* **Using a library like Lodash**: Lodash provides a `forEach` function that can be used to iterate over arrays, eliminating the need for individual event listeners.
* **Using a framework or async/await**: Some frameworks and libraries provide built-in support for handling arrays of callbacks in an asynchronous manner.

In summary, the benchmark compares two approaches to handling arrays of callbacks in JavaScript: individual event listeners vs. a single event listener with an array of callbacks. The choice between these approaches depends on factors such as memory usage, performance requirements, and code complexity.

1000 x event listeners vs single event listener with array of 1000 callbacks (version: 0)

Comparing performance of: `1000 event listeners vs 1 event listener handling an array of 1000 callbacks`

Created: 3 years ago by: Guest

Go to the latest result

1000 event listeners

1 event listener handling an array of 1000 callbacks

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

1000 x event listeners vs single event listener with array of 1000 callbacks (version: 0)

Comparing performance of: 1000 event listeners vs 1 event listener handling an array of 1000 callbacks

Created: 3 years ago by: Guest

Go to the latest result

1000 event listeners

1 event listener handling an array of 1000 callbacks

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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Comparing performance of: `1000 event listeners vs 1 event listener handling an array of 1000 callbacks`