Benchmark: var vs document.body

HTML Preparation code:

<div class="test"></div>
<div class="test2"></div>
<div class="test3"></div>

Tests:

var
var db = document.body; db.querySelectorAll(".test") db.querySelectorAll(".test2") db.querySelectorAll(".test3")
document.body
var db = document.body; document.body.querySelectorAll(".test") document.body.querySelectorAll(".test2") document.body.querySelectorAll(".test3")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
var
document.body

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.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The test case is comparing two approaches to access the `document.body` element in JavaScript:

1. Using the `var` keyword to declare a variable, assigning it the value of `document.body`, and then calling the `querySelectorAll()` method on that variable.
2. Directly accessing the `document.body` element without declaring a variable.

**Options Compared**

The two options being compared are:

* Option 1: Using a variable (`var db = document.body`) to access the `document.body` element, followed by multiple calls to `querySelectorAll()`.
* Option 2: Directly accessing the `document.body` element and calling `querySelectorAll()` multiple times.

**Pros and Cons of Each Approach**

**Option 1 (Using a variable)**

Pros:

* May be more efficient due to the caching mechanism in modern browsers, which can reduce the number of DOM queries.
* Can make code easier to read and maintain by encapsulating the DOM access logic in a variable.

Cons:

* May introduce unnecessary overhead due to the creation of a new variable.
* Can lead to confusion if the variable is not properly scoped or cleared.

**Option 2 (Directly accessing `document.body`)**

Pros:

* Has minimal overhead, as it directly accesses the DOM element without creating an additional variable.
* Can be beneficial for simple cases where the direct access is faster and more efficient.

Cons:

* May lead to duplicated code if multiple instances of `querySelectorAll()` need to be called on different elements.
* Can make code harder to read and maintain due to repeated method calls.

**Library Usage**

The test case uses the `querySelectorAll()` method, which is a standard method in the DOM API. This method is used to select all descendant elements that match a specified CSS selector. In this case, it's used to select all elements with the class "test", "test2", and "test3".

**Special JS Feature/Syntax**

There doesn't appear to be any specific JavaScript feature or syntax being tested in this benchmark.

**Other Considerations**

When testing performance-critical code like this, several other factors can impact results, including:

* Cache effectiveness: Modern browsers have various caching mechanisms that can affect the performance of repeated DOM queries.
* Browser-specific optimizations: Different browsers may optimize their JavaScript engines differently, leading to varying performance characteristics.
* Hardware and system configuration: The test environment's hardware, operating system, and system configuration can influence the results.

**Alternative Approaches**

If you want to explore alternative approaches or variations on this benchmark, consider:

* Using other DOM query methods, such as `getElementsByClassName()` or `querySelector()`, to compare their performance.
* Introducing additional complexity by using nested selectors, pseudo-classes, or attributes.
* Testing with different browser versions or configurations to assess browser-specific optimizations.
* Adding more elements to the HTML template to increase the number of DOM queries and make the benchmark more realistic.

Related benchmarks:

var vs document.body (version: 0)

Comparing performance of: var vs document.body

Created: 8 years ago by: Guest

Jump to the latest result

var

document.body

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):