Benchmark: querySelectorAll2 vs getElementsByClassName

HTML Preparation code:

<div class="test"></div>

Tests:

querySelector
document.querySelectorAll(".test")
getElementsByClassName
document.getElementsByClassName(".test")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided benchmark is designed to compare the performance of two DOM query methods in JavaScript: `querySelectorAll` and `getElementsByClassName`. The goal is to measure which method is faster for retrieving elements from an HTML document.

**Options Compared**

There are two options being compared:

1. **`document.querySelectorAll('.test')`**: This method returns a NodeList containing all elements with the specified CSS selector, `.test`.
2. **`document.getElementsByClassName('test')`**: This method returns a HTMLCollection containing all elements with the specified class name, `test`.

**Pros and Cons of Each Approach**

**`document.querySelectorAll('.test')`**

Pros:

* More flexible and powerful than `getElementsByClassName`, as it allows for more complex selectors.
* Can be used to select elements based on various attributes and pseudo-classes.

Cons:

* May have a higher overhead due to the need to parse the CSS selector.
* Can return an empty NodeList if no elements match the selector.

**`document.getElementsByClassName('test')`**

Pros:

* Simpler and faster than `querySelectorAll`, as it only needs to check for class names.
* Returns a HTMLCollection, which can be more efficient in some cases.

Cons:

* Less flexible and powerful than `querySelectorAll`, as it only checks for exact class names.
* May not work well with CSS pseudo-classes or attribute selectors.

**Other Considerations**

* The benchmark does not account for the number of elements returned by each method, which could affect performance. For example, if many elements match the selector, `querySelectorAll` may still be faster due to its ability to return a large array at once.
* The benchmark is focused on desktop browsers (Chrome 102) and Windows operating systems. Results may vary for other platforms.

**Library Usage**

There are no libraries used in this benchmark.

**Special JS Features/Syntax**

None mentioned.

**Benchmark Preparation Code**

The preparation code consists of:

```javascript
"<div class=\"test\"></div>"
```

This is a simple HTML element with the class name `test`, which will be used as the target for the DOM queries.

**Individual Test Cases**

There are two test cases:

1. **`document.querySelectorAll('.test')`**: Tests the performance of `querySelectorAll` with a CSS selector that matches an existing element.
2. **`document.getElementsByClassName('test')`**: Tests the performance of `getElementsByClassName` with a class name that exactly matches an existing element.

**Latest Benchmark Result**

The latest benchmark result shows that:

* `getElementsByClassName` performs better than `querySelectorAll` in this specific test case, with 1530314.5 executions per second compared to 2510163.5.
* The results are consistent across different browser and device platforms.

**Alternatives**

Some alternatives to these methods include:

* Using `querySelector` or `querySelectorAll` with a more specific CSS selector, such as `.test:not(.other-class)`.
* Using a library like jQuery or Zepto, which provide faster and more flexible DOM query methods.
* Using a framework like React or Angular, which often use optimized DOM query methods.

Related benchmarks:

querySelectorAll2 vs getElementsByClassName (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 3 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

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):