Benchmark: querySelector vs querySelectorAll vs getElementsByClassName vs querySelector (ID) vs getElementsByID Corrected+

HTML Preparation code:

<div class="test" id="test" data-x></div>

Tests:

querySelector
document.querySelector(".test")
querySelectorAll
document.querySelectorAll(".test")
getElementsByClassName
document.getElementsByClassName("test")
querySelector (ID)
document.querySelector("#test")
getElementsByID
document.getElementById("test")
querySelectorAll+
document.querySelectorAll("[data-x]")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
querySelectorAll
getElementsByClassName
querySelector (ID)
getElementsByID
querySelectorAll+

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/109.0.0.0 Safari/537.36

Browser/OS: Chrome 109 on Windows

View result in a separate tab

Test name	Executions per second
querySelector	8650168.0 Ops/sec
querySelectorAll	2315579.2 Ops/sec
getElementsByClassName	14549909.0 Ops/sec
querySelector (ID)	4767273.0 Ops/sec
getElementsByID	22500926.0 Ops/sec
querySelectorAll+	1430627.8 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 months ago):

LLMs can make mistakes. Check important info.

The benchmark you provided evaluates the performance of various DOM querying methods in JavaScript for selecting HTML elements. Each method has different characteristics and performance implications, which can be useful for developers to understand when optimizing their web applications.

### Overview of Tested Methods:

1. **document.querySelector(".test")**
   - **Test Name**: `querySelector`
   - **Description**: This method returns the first element that matches the specified CSS selector (`.test` in this case).
   - **Pros**: Supports all CSS selectors, which allows for complex queries.
   - **Cons**: Slower than other methods when targeting specific IDs or class names due to CSS selector parsing.

2. **document.querySelectorAll(".test")**
   - **Test Name**: `querySelectorAll`
   - **Description**: This returns a NodeList of all elements matching the provided CSS selector. 
   - **Pros**: Great for retrieving all matched elements at once.
   - **Cons**: Similar to `querySelector`, it can be slower due to complex selector parsing, and the returned NodeList is static.

3. **document.getElementsByClassName("test")**
   - **Test Name**: `getElementsByClassName`
   - **Description**: This method returns a live HTMLCollection of elements with the specified class name.
   - **Pros**: Faster than query methods when selecting by class name; it returns a live collection that updates automatically with DOM changes.
   - **Cons**: Limited to class selectors only and cannot support complex CSS selectors.

4. **document.querySelector("#test")**
   - **Test Name**: `querySelector (ID)`
   - **Description**: This method selects the first element with the ID `test`.
   - **Pros**: Similar benefits as `querySelector`, but since IDs are unique, it tends to be faster than class selections.
   - **Cons**: Only works for IDs, thus limited in scope.

5. **document.getElementById("test")**
   - **Test Name**: `getElementsByID`
   - **Description**: This method retrieves the element with the specified ID.
   - **Pros**: The fastest method of selecting elements, since it directly accesses the element by its unique ID.
   - **Cons**: Limited to selecting only one element by ID.

6. **document.querySelectorAll("[data-x]")**
   - **Test Name**: `querySelectorAll+`
   - **Description**: This selects all elements with the `data-x` attribute.
   - **Pros**: Allows querying based on custom attributes, supporting broader usage.
   - **Cons**: Similar performance concerns as `querySelectorAll`.

### Performance Results
From the benchmark results, we observe the following executions per second:
- `getElementsByID`: **22,500,926**
- `getElementsByClassName`: **14,549,909**
- `querySelector`: **8,650,168**
- `querySelector (ID)`: **4,767,273**
- `querySelectorAll`: **2,315,579**
- `querySelectorAll+`: **1,430,627**

### Summary of Findings
The fastest method was `getElementById`, which is expected as it directly accesses an element via its unique identifier. `getElementsByClassName` also performed well, leveraging direct class-based lookups. Conversely, methods allowing CSS selector syntax (`querySelector` and `querySelectorAll`) performed relatively slower due to their capability to handle complex selections.

### Considerations for Developers
When choosing which method to use, developers should consider:
- **Performance Requirements**: For high-performance situations, prefer `getElementById` or `getElementsByClassName`.
- **Complexity of Selection**: Use `querySelector` or `querySelectorAll` for more complex queries involving multiple conditions or CSS selectors.
- **Dynamic Updates**: If you need elements that will update with DOM changes, `getElementsByClassName` can be beneficial due to its live HTMLCollection.

### Alternatives
Alternatives to JavaScript DOM querying methods include:
- **jQuery**: An older library which provides a simpler syntax for DOM manipulation and querying but may have performance overhead compared to native methods.
- **Frameworks like React or Vue**: These use virtual DOMs and abstract the querying process, providing their mechanisms for rendering and selecting elements.
- **Pure DOM methods**: Utilizing lower-level API calls allowing for batch updates and optimized queries, such as `documentFragment`.

Understanding the differences between these methods and their optimal usage will enable developers to write efficient and performant code in their applications.

Related benchmarks:

querySelector vs querySelectorAll vs getElementsByClassName vs querySelector (ID) vs getElementsByID Corrected+ (version: 1)

Comparing performance of: querySelector vs querySelectorAll vs getElementsByClassName vs querySelector (ID) vs getElementsByID vs querySelectorAll+

Created: 2 months ago by: Guest

Jump to the latest result

querySelector

querySelectorAll

getElementsByClassName

querySelector (ID)

getElementsByID

querySelectorAll+

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 months ago):