@lew 
To style an iframe in React.js, you can use CSS within your component's styling or use inline styles.
In your CSS file:
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iframe {
  width: 100%;
  height: 400px;
  border: 1px solid black;
}
 | 
In your React component:
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import React from 'react';
import './iframeStyles.css'
const MyComponent = () => {
  return (
    <div>
      <iframe src="https://www.example.com" title="example"></iframe>
    </div>
  );
}
export default MyComponent;
 | 
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import React from 'react';
const MyComponent = () => {
  const iframeStyles = {
    width: '100%',
    height: '400px',
    border: '1px solid black'
  };
  return (
    <div>
      <iframe src="https://www.example.com" title="example" style={iframeStyles}></iframe>
    </div>
  );
}
export default MyComponent;
 | 
By using either of these methods, you can easily style the iframe in your React component according to your preferences.