useRef.js

const App = () => {
  const [value, setValue] = React.useState('highlight and copy me');
  const textInput = React.useRef();
  
  const handleClick = () => {
    textInput.current.select();
    document.execCommand('copy');
  }
  
  return (
    <div>
      <input type="text" ref={textInput} readOnly value={value}/>
      <button onClick={handleClick}>Copy</button>
    </div>
  );
};