HTMLCollection vs NodeList – What's the Difference?

 

In the context of the Document Object Model (DOM) in JavaScript, both `HTMLCollection` and `NodeList` are array-like objects that contain sets of DOM nodes or elements. However, there are subtle differences between them:

HTMLCollection:

Live Collection: `HTMLCollection` is a live collection, meaning it's automatically updated when the DOM changes. If elements are added or removed from the DOM, the `HTMLCollection` updates itself automatically to reflect those changes.

Limited Methods: It offers a limited set of methods and properties compared to `NodeList`.

Specific to Elements: `HTMLCollection` is mainly used to represent collections of HTML elements by name, ID, or tag name, typically obtained via methods like `getElementsByTagName()`, `getElementsByClassName()`, or accessing properties like `form.elements`.

Example:

const elementsByTagName = document.getElementsByTagName('div');

console.log(elementsByTagName instanceof HTMLCollection); // true

NodeList:

Static Collection: `NodeList` is a static collection, meaning it does not update itself automatically when the DOM changes. Once created, it remains unchanged even if the DOM is modified.

More Methods: `NodeList` offers a broader range of methods and properties compared to `HTMLCollection`. It includes methods like `forEach()`, `item()`, and `keys()` that allow easier traversal and manipulation of node lists.

Returned by Various Methods: `NodeList` can be returned by various DOM methods like `querySelectorAll()`, `childNodes`, or `parentNode.childNodes`. It can contain various node types, not limited to elements.

Example:

const nodeList = document.querySelectorAll('div');

console.log(nodeList instanceof NodeList); // true

Summary of Differences:

Mutability: `HTMLCollection` is live (mutable) and updates automatically with DOM changes, while `NodeList` is static and doesn't update.

Methods: `NodeList` has a broader range of methods for traversal and manipulation compared to `HTMLCollection`.

Use Cases: `HTMLCollection` is often associated with specific element collections, whereas `NodeList` can contain various node types beyond elements.

In practice, when selecting elements from the DOM, `NodeList` is more versatile and offers a broader range of methods for working with the selected nodes. However, both `HTMLCollection` and `NodeList` have their use cases based on the specific requirements of DOM manipulation.