.getElementsByClassName() retrieves a "live" node list, which is a collection of nodes in the Document Object Model.
This node list behaves like an "array-like" object and can be iterated over.
However, .getElementsByClassName() is an outdated API that causes the DOM to be re-scanned upon each access, affecting performance. It should be used sparingly, if at all.
The code snippet you provided:
var x = document.getElementsByClassName("example");
x[0].innerHTML = "Hello World!";
shows accessing the first node in the node list returned by .getElementsByClassName() and updating its content with .innerHTML.
Instead of scanning the entire DOM, you can use .querySelector() to find the first matching element.
A better approach is to use .querySelectorAll() as a modern replacement, which returns a static node list for better performance.
For example, to achieve the same result as the code snippet you shared:
// Find the first node with the example class and set its text to "Hello World!"
var x = document.querySelector(".example").textContent = "Hello World!";
It's recommended to refer to reliable sources like The Mozilla Developers Network for up-to-date information on web development.