const doFetch = (url, data) => { var load = document.getElementById('loading'); load.style.display = "flex"; var post = Object.assign({ credentials: 'same-origin'}, data); return fetch(url, data) .then(response => { load.style.display = "none"; if (response.headers.get('Content-Type') === 'application/json') { return response.json(); } return response.text(); } ) }