https://stackoverflow.com/questions/51800031/react-nodejs-http-always-send-options-instead-regular-methods?noredirect=1#comment90559507_51800031

clientFetch.js

onSaveClicked = () => {
    const options = {
        crossDomain: true,
        credentials: 'include',
        method: 'PUT',
        headers: {
          'Content-Type': 'application/json',   
        },
        body: {
            filename: this.state.name
        }
    };
    fetch('http://localhost:3000/api/manage/privacy', options)
        .then(res => {
          const jsonResp = res.json();
          console.log(jsonResp);
          this.setState({ files: jsonResp.result });
        })
        .catch(console.error)
}