JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.3.1/react.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.3.1/react-dom.js"></script>
<div id="root">
  <!-- This div's content will be managed by React. -->
</div>

CSS

.no-borderRadius {
  border-radius: 0px;
}

.no-borderRadiusImportant {
  border-radius: 0px !important;
}

 .border-radiusImportant{
   border: 1px solid black;
   border-radius: 5px !important;
 }

Babel + JSX

ReactDOM.render(
  <div>
  <div className="no-borderRadius" style={{border: '1px solid black',borderRadius: '5px'}}>Hello, world!</div>
  <div className="no-borderRadiusImportant" style={{border: '1px solid black',borderRadius: '5px'}}>Hello, world!</div>
  <div className="no-borderRadiusImportant" style={{border: '1px solid black',borderRadius: '5px!important'}}>Hello, world!</div>
  <div className="no-borderRadiusImportant border-radiusImportant">Hello, world!</div>
  </div>,
  document.getElementById('root')
);