Enter our friend, JavaScript. If JavaScript is going to be the muscles of the body, it's then responsible for manipulating the bones (HTML) and the skin (CSS). Our human muscles can't do all that much to change our physical appearance, but they can certainly put us in different positions, expanding and contracting our elastic skin and manipulating the positions of our bones. With JavaScript, it's possible to rearrange content on a page, change colors, create animations, and much more. We'll be diving deeply into how JavaScript interacts with HTML and CSS because, after all, JavaScript is why we're here now, reading this book!
One of the most notable points to make about JavaScript versus Python is that, in order to make changes to a page, a Pythonic program would have to respond to input from the client side from the server, and then the browser would re-render the HTML. JavaScript avoids this by executing in the browser.
For example, in our page shown...
