Trying to use React.DOM to set body styles

Assuming your body tag isn't part of another React component, just change it as usual:

document.body.style.backgroundColor = "green";
//elsewhere..
return (
  <div>
    Stuff goes here.
  </div>
);

It's recommended to put it at componentWillMount method, and cancel it at componentWillUnmount:

componentWillMount: function(){
    document.body.style.backgroundColor = "green";
}

componentWillUnmount: function(){
    document.body.style.backgroundColor = null;
}

With functional components and useEffect hook :

useEffect(()  => {
    document.body.classList.add('bg-black');

    return () => {
        document.body.classList.remove('bg-black');
    };
});

A good solution to load multiple atributes from a js class to the document body can be:

componentWillMount: function(){
    for(i in styles.body){
        document.body.style[i] = styles.body[i];
    }
},
componentWillUnmount: function(){
    for(i in styles.body){
        document.body.style[i] = null;
    }
},

And after you write your body style as long as you want:

var styles = {
    body: {
        fontFamily: 'roboto',
        fontSize: 13,
        lineHeight: 1.4,
        color: '#5e5e5e',
        backgroundColor: '#edecec',
        overflow: 'auto'
    }
}