Iam a little bit late maybe, but I found a solution, what I did, I add it in css page, then inspect the element.
For example : for * background: linear-gradient(to right, #000 0%, #000 50%, #fff 50% #fff 100%)*; if you inspect it using inspect element, you will find : -webkit-gradient(linear, left top, right top, from(#000), color-stop(50%, #000), color-stop(50%, #fff)) .
So just add this last line in the inline style of your react compenent:
<div className="card" style={{background:"-webkit-gradient(linear, left top, right top, from(#000), color-stop(50%, #000), color-stop(50%, #fff))"}}/>
for my example, I used this one above instead of :
<div className="card" style={{background: linear-gradient(to right, #000 0%, #000 50%, #fff 50% #fff 100%)"}}/>
So in conclusion, add this to a css file, it will work, see the output in the "inspect element", and use it and edit it as you like in the inline style of your react js component.