Benchmark: querySelector-2 - MeasureThat.net

HTML Preparation code:

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Script Preparation code:

x = 0;

Tests:

querySelector with misses
let n = (Math.random() * 45) | 0; x = document.querySelector("#blahblah-" + n);
getElementById with misses
let n = (Math.random() * 45) | 0; x = document.getElementById("blahblah-" + n);
querySelector without misses
let n = (Math.random() * 40) | 0; x = document.querySelector("#blahblah-" + n);
getElementById without misses
let n = (Math.random() * 40) | 0; x = document.getElementById("blahblah-" + n);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector with misses
getElementById with misses
querySelector without misses
getElementById without misses

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its results.

**What is being tested?**

MeasureThat.net is testing two methods for selecting elements in an HTML document: `document.querySelector` and `document.getElementById`. The tests are designed to measure the performance of these methods under various scenarios, specifically when there are random misses (i.e., the selector does not match any element).

**Options compared**

There are four test cases:

1. `querySelector with misses`: This test uses a random selector that may or may not match an existing element in the document.
2. `getElementById with misses`: Similar to the previous test, but this time using `document.getElementById` instead of `document.querySelector`.
3. `querySelector without misses`: In this case, the selector is guaranteed to match an existing element in the document.
4. `getElementById without misses`: Again, a guarantee that the selector will match an existing element.

**Pros and cons of each approach**

1. **querySelector with misses**:
	* Pros: This method can be faster than `document.getElementById` when there are many elements with matching selectors, since it only needs to traverse a subset of the DOM.
	* Cons: The performance can degrade significantly if there are no matches, as the browser has to perform more work to find an existing element.
2. **getElementById with misses**:
	* Pros: This method is more predictable and reliable than `querySelector`, especially when there are many elements with matching IDs.
	* Cons: It can be slower for large numbers of elements due to the need to traverse the entire DOM.
3. **querySelector without misses**:
	* Pros: When the selector guarantees a match, this method can be faster than `document.getElementById` since it only needs to find an existing element.
	* Cons: The performance may not be as good as `document.getElementById` when there are no matches, since the browser has to perform more work to traverse the DOM.
4. **getElementById without misses**:
	* Pros: This method is similar to the previous one but uses `querySelector` instead of `getElementById`.
	* Cons: Same as above.

**Other considerations**

The results also depend on the specific browser, device platform, and operating system being used. In this case, Chrome 71 on Linux Desktop shows a pattern:

* `querySelector with misses`: Slower than expected (due to potential performance issues when there are no matches)
* `getElementById with misses`: Faster but still slower than expected
* `querySelector without misses`: Very fast due to the guarantee of finding an existing element
* `getElementById without misses`: Similar to the previous one but using `querySelector` instead

**Benchmark results**

The current benchmark results show:

1. `querySelector with misses`: 264843.25 executions per second (lower than expected)
2. `getElementById with misses`: 509181.1875 executions per second (faster than expected)
3. `querySelector without misses`: 267294.71875 executions per second (very fast)
4. `getElementById without misses`: Similar to the previous one but using `querySelector` instead.

In summary, the results suggest that when there are no matches, `document.getElementById` can be faster than `document.querySelector`. However, when there is a guarantee of finding an existing element, `document.querySelector` can be much faster.

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36

Browser/OS: Chrome 71 on Linux

View result in a separate tab

Test name	Executions per second
querySelector with misses	264843.2 Ops/sec
getElementById with misses	525069.0 Ops/sec
querySelector without misses	267294.7 Ops/sec
getElementById without misses	509181.2 Ops/sec

Related benchmarks:

querySelector-2 (version: 0)

Comparing performance of: querySelector with misses vs getElementById with misses vs querySelector without misses vs getElementById without misses

Created: 5 years ago by: Registered User

Jump to the latest result

querySelector with misses

getElementById with misses

querySelector without misses

getElementById without misses

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):