Benchmark: QuerySelector vs QuerySelectorAll + forEach for 1 element

HTML Preparation code:

<div id='hello'></div>
<div id='there'></div>

Tests:

QuerySelector
console.log(document.querySelector('#hello'));
QuerySelectorAll + ForEach
document.querySelectorAll('#hello').forEach((el) => { console.log(el); });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
QuerySelector
QuerySelectorAll + ForEach

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Windows

View result in a separate tab

Test name	Executions per second
QuerySelector	323929.5 Ops/sec
QuerySelectorAll + ForEach	283805.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark test.

**What is being tested?**

The benchmark is testing two approaches to select and log an element from HTML:

1. `console.log(document.querySelector('#hello'));`: This approach uses the `querySelector` method, which selects the first element that matches the specified CSS selector.
2. `document.querySelectorAll('#hello').forEach((el) => { console.log(el); });`: This approach uses the `querySelectorAll` method to select all elements that match the specified CSS selector, and then iterates over the result using the `forEach` method, logging each element.

**What options are being compared?**

The two approaches being tested are:

* Using `querySelector` (Approach 1)
* Using `querySelectorAll` followed by `forEach` (Approach 2)

**Pros and Cons of each approach:**

**Approach 1: `console.log(document.querySelector('#hello'));`**

Pros:

* Simple and concise
* Fast, since it only needs to select one element

Cons:

* May not find the expected element if there are multiple elements with the same selector (it will return the first one)
* Does not log all matching elements, just the first one

**Approach 2: `document.querySelectorAll('#hello').forEach((el) => { console.log(el); });`**

Pros:

* Logs all matching elements
* Handles cases where there are multiple elements with the same selector

Cons:

* More complex and verbose than Approach 1
* May be slower since it needs to select all elements and then iterate over them

**Other considerations:**

* Using `querySelectorAll` followed by `forEach` can be less efficient if only one element matches the selector, as it will still perform a full query.
* In modern JavaScript, it's often preferred to use `Array.prototype.forEach.call()` or a for...of loop instead of vanilla `forEach`, which provides better support for handling arrays and other iterable objects.

**Library usage:**

In this benchmark, no libraries are explicitly used. However, the `document` object is part of the browser's DOM (Document Object Model), which is a built-in JavaScript API.

**Special JS features or syntax:**

There are no special JavaScript features or syntax mentioned in this benchmark. The test only uses standard JavaScript methods and properties, such as `querySelector`, `querySelectorAll`, `forEach`, and `console.log`.

**Alternatives:**

Other alternatives to the two approaches being tested could include:

* Using `Array.prototype.find()` or a similar method to find the first matching element
* Using a library like Lodash to handle array-like objects and provide more concise methods for iterating over them
* Using a more efficient querying method, such as CSS selectors with attribute filtering (e.g., `document.querySelector('#hello[attr="value"]')`)

Keep in mind that these alternatives may not be relevant or applicable to all use cases, and the benchmark's focus is on comparing two specific approaches.

Related benchmarks:

QuerySelector vs QuerySelectorAll + forEach for 1 element (version: 0)

Comparing performance of: QuerySelector vs QuerySelectorAll + ForEach

Created: 5 years ago by: Guest

Jump to the latest result

QuerySelector

QuerySelectorAll + ForEach

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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