The querySelectorAll() method in JavaScript returns a static (not live) NodeList of all elements that match the given CSS selector. This means that the NodeList is a snapshot of the elements that matched the selector at the time the method was called, and it will not update if the DOM (Document Object Model) changes.

In contrast, the getElementsBy* methods (such as getElementsByTagName() and getElementsByClassName()) return a live HTMLCollection of elements that match the given criteria. This means that the HTMLCollection will update automatically if the DOM changes, so the list of elements it contains will always be up-to-date.

Here's an example that shows how you can use querySelectorAll() and getElementsByClassName() to select elements from the DOM:




In this example, querySelectorAll() and getElementsByClassName() both return a list of div elements that have the class my-class. However, the nodeList is a static snapshot of the elements, whereas the htmlCollection is a live list that will update automatically if the DOM changes.

One key difference between a NodeList and an HTMLCollection is that a NodeList is an array-like object, which means you can use array methods like forEach() and map() on it. In contrast, an HTMLCollection is not an array, so you can't use array methods on it directly. However, you can convert an HTMLCollection to an array using the Array.from() method, like this



Another difference between these two types of collections is that a NodeList is "live" in the sense that it updates automatically if the DOM changes, whereas an HTMLCollection is not. This means that if you add or remove elements from the DOM, the NodeList will reflect those changes, but the HTMLCollection will not.

For example, let's say you have a div element with the class my-class, and you use querySelectorAll() to select all elements with that class:



Hope i was able to give some insights on the matter.Cheers! Happy coding!!!