How can styles or classes be changed in elements using JavaScript?

To modify the styles of all items belonging to a particular class:

     To obtain a collection of the elements with the  specified class, use the querySelectorAll() method.

Iterate through the  collection using the forEach() method.

In HTML, the class name is used as a selector, which helps to give the element attributes some value. The element in the document with the "id" attribute can be obtained using the document.getElementById() method, and the element's class can be modified or added using the "className" attribute.