In real practice, how often do you change the design/color via JS?

If the design is static, you would indeed most likely implement it in CSS.

JavaScript is primarily used to make changes happen while the page is being viewed, perhaps in response to some action by the user.

Hi wwyattw,

Using JavaScript to change a colour of an element is probably not a great idea in most genuine use case scenarios, because it won't lead to developing an easily updatable codebase for your project.

It's more likely that you'll establish CSS rules for each state of an element - say, a "front" and a "reverse" state for a div you want to turn into a card that flips over when a user clicks it. You'll then just be using JS to switch between the two.

However, during the process of building a project, I often use JS's ability to make a colour/design change in order to take a step closer toward that final output. It helps me check something is working as I expect.

Furthermore, if you're coding something that's very simple - like a script to highlight any element that your mouse hovers over, then it may be easier just to define the colour changes right inside the JavaScript rather than worry about defining CSS styles for it.

I guess it depends on how you want to organise your code - the beauty of JavaScript is that it's very flexible and has control over all of the elements on your page that HTML and CSS do... it's up to you to decide how to use it.