getElementBy*() vs. querySelector() – Choosing the Right Method

In the world of web development, manipulating HTML elements is essential, and JavaScript provides two common methods for selecting elements: getElementBy*() and querySelector(). Both are widely used but differ in syntax, functionality, and performance. When deciding which method to use, it’s important to understand their differences to make the right choice for your project. In this guide, we’ll explore both methods and discuss their advantages, so you can choose the most efficient one for your needs.

In this section, we’ll cover the following topics:

getElementBy Methods

The getElementBy*() methods offer a straightforward approach to target elements by attributes such as ID, class, name, or tag name. These methods remain valuable in many contexts, especially when performance is a priority or in older browser environments. Though querySelector() is often preferred for its flexibility, getElementBy*() methods continue to be effective and relevant. Let’s explore the specific methods available.

getElementById()

getElementById() is one of the most commonly used methods in JavaScript. It allows developers to select a single element based on its unique ID attribute. This method returns the first element it finds with the specified ID, making it very efficient for targeting individual elements.

Example:

let element = document.getElementById("myElement");

This method is case-sensitive and should always be used with a valid ID for best results.

getElementsByClassName()

getElementsByClassName() allows you to select elements by their class name. Unlike getElementById(), this method can return multiple elements, as multiple elements on a page can share the same class. It returns a live HTMLCollection, meaning the collection updates automatically if the DOM changes.

Example:

let elements = document.getElementsByClassName("myClass");

getElementsByName()

getElementsByName() selects elements based on their name attribute. This method is commonly used for form elements like input fields, radio buttons, or checkboxes. Like getElementsByClassName(), it returns a live HTMLCollection.

Example:

let elements = document.getElementsByName("myFormElement");

getElementsByTagName()

getElementsByTagName() targets elements based on their tag name, such as <div>, <span>, or <p>. This method also returns a live HTMLCollection and can be useful when you want to select all elements of a specific type.

Example:

let elements = document.getElementsByTagName("div");

getElementsByTagNameNS()

getElementsByTagNameNS() is similar to getElementsByTagName(), but it allows you to filter by namespace as well. This method is less commonly used and is primarily relevant when working with XML or SVG documents, where namespaces play a key role in element identification.

Example:

let elements = document.getElementsByTagNameNS(
  "http://www.w3.org/2000/svg",
  "circle"
);

querySelector Methods

querySelector() and querySelectorAll() are modern methods for selecting elements using CSS selectors. They offer unparalleled flexibility compared to getElementBy*() methods, as they allow developers to use CSS-like syntax to target elements. While similar, these two methods have key differences in their behavior and use cases.

querySelector()

The querySelector() method selects the first matching element in the DOM based on the provided CSS selector. This makes it suitable when you only need a single element, regardless of whether there are multiple matches.

Example:

let element = document.querySelector(".myClass");

In this example, only the first element with the class myClass will be selected, even if multiple elements share the same class.

Key Features:

• Returns only one element, even if more elements match the selector.
• Stops searching once the first match is found, making it slightly faster for single-element selection.
• Ideal for unique elements or when only the first match is relevant.

querySelectorAll()

querySelectorAll() is designed to return all matching elements in the DOM as a static NodeList. Unlike querySelector(), which stops at the first match, querySelectorAll() continues searching and includes every element that matches the CSS selector.

Example:

let elements = document.querySelectorAll(".myClass");

In this example, all elements with the class myClass will be selected and returned as a NodeList.

Key Features:

• Returns a static NodeList of all matching elements.
• Allows iteration through multiple elements, making it ideal for batch operations or when styling or applying logic to a group of elements.
• The returned NodeList is static, meaning it does not update automatically if the DOM changes after selection.

Summary of Differences

By understanding these distinctions, developers can choose the method that best fits their needs, ensuring efficiency and clarity in their code. For single-element operations, querySelector() is the go-to choice, while querySelectorAll() is better suited for tasks involving multiple elements.

getElementBy vs. querySelector

Choosing between getElementBy*() methods and querySelector() depends on your specific use case. Both have their strengths and limitations, so it’s essential to understand when to use each one.

• Flexibility: querySelector() is far more flexible than getElementBy*() methods. It supports a wide range of CSS selectors, including pseudo-classes and attribute selectors, making it a better choice for complex or dynamic DOM structures. In contrast, getElementBy*() methods are more limited, as they can only select by ID, class, name, or tag.
• Multiple Elements: If you need to select multiple elements, getElementsByClassName() or getElementsByTagName() can still be useful. However, they return live collections, meaning the list is updated automatically when the DOM changes. querySelectorAll() returns a static NodeList, which is often preferred when you don’t need real-time updates.
• Ease of Use: querySelector() is typically easier to use, especially for developers familiar with CSS syntax. It allows you to use the same selector strings you're accustomed to in CSS, making the code more readable and concise.
• Performance: While it's often claimed that getElementBy*() methods are faster, the performance difference between these methods and querySelector() is typically negligible in real-world applications. Modern browsers have optimized querySelector() to perform efficiently, even with complex selectors. Unless you're working with extremely large DOMs or need to select elements repeatedly in a performance-critical context, the speed difference is not usually significant.

In conclusion, while getElementBy*() methods are still perfectly valid and have their place in performance-sensitive situations, querySelector() is the more flexible and modern option. For most use cases, querySelector() or querySelectorAll() is the recommended method, although the getElementBy*() methods continue to be useful in certain contexts, especially when backward compatibility or simplicity is a priority.

Reference links:

getElementById() on MDN

querySelector() on MDN