I would like to count the length of my response JSON. Here's my code:

getMoviesFromApiAsync() {

return fetch('http://sampleurl.com/' + CommonDataManager.getInstance().getUserID())

    .then((response) => response.json())

    .then((responseJson) => {

        this.setState({isLoading: false, listMessages: responseJson});    

    })

    .catch((error) => {

        console.error(error);

    });

}