title: Add a class to the HTML <body> tag with React?
body: <p>I'm making a modal in my React project that requires a class to be added to the body when the modal is open and removed when it is closed.</p>
  <p>I could do this the old jQuery way by running some vanilla JavaScript which adds / removes a class, however this doesn't feel like the normal React philosophy.</p>
  <p>Should I instead setState on my top level component to say whether the modal is open or closed? Even if I did this, as it's rendered into the div on the page it's still a side-effect to edit the body element, so is there any benefit for this extra wiring?</p>