How select part of text in a Textfield on onFocus event with material-UI in React?

I have a modal form with material -UI TextField in react app, I have a default value, es. a file, and i would select only the name of the file no the extension when the element is load….

I did this code inside the tag TextField:

<textField 
    value={value}
    fullWidth
    autoFocus
    onFocus={event => {
    event.target.select()}} />

but this will select all text inside the textField. How can I select only a part of the text? ex: if i have myfile.doc i would be selected only myfile like this

Thanks

Answer

Use the setSelectionRange in combination with the lastIndexOf method to find the position of the last ..

class App extends React.Component {
  handleFocus = event => {
    event.preventDefault();
    const { target } = event;
    const extensionStarts = target.value.lastIndexOf('.');
    target.focus();
    target.setSelectionRange(0, extensionStarts);
  }
  
  render(){
    return (
      <input
        value={'myfile.doc'}
        onFocus={this.handleFocus}
      />
    )
  }
}

ReactDOM.render(<App />, document.getElementById('root'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="root"></div>