JS: How to add or remove a class and make your sites interactive

Hello World! New episode of the series - A CSS/JS trick in 5 minutes.
Today we will quickly see how to manipulate a class throw javascript (add, remove and check presence).

In reality, you have to imagine classes as a list, all elements in a page have is own list of class you can modify with javascript. So if you want to modify an element you don't need to do all the stuff (it's much longer and boring) with javascript. You just have to define a class in CSS with all the attributes then add this class to the element(s) you want to modify. So for example you can have a live element update on scrolling

Add

  let foo = document.querySelector("#foo");
  element.classList.add("newClass");

Remove

 foo.classList.remove("classToRemove");

You can also check if an element contains a class (and then perform operations with the boolean result):

  foo.classList.contains('AreYouHere')

Hope this helped and thanks for reading!

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Check this article about how to write CSS like a pro!