Fetch for old browsers

request.js

/**
 * Small request wrapper for XMLHttpRequest
 * with an API similar to fetch.
 *
 * @author Gabe M.
 * @param {string} url - Resource Url for Request
 * @param {Object} config
 * @param {string} [config.method=GET] - REST request method
 */
function request(url, { method = 'GET' } = {}) {
    return new Promise((resolve, reject) => {
        const req = new XMLHttpRequest();

        req.onload = () => {
            if (req.status >= 200 && req.status < 300) {
                resolve({
                    status: req.status,
                    statusText: req.statusText,
                    text: () => Promise.resolve(req.responseText),
                    json: () =>
                        Promise.resolve(req.responseText).then(JSON.parse),
                });
            } else {
                reject(new Error(req.statusText));
            }
        };
        req.onerror = reject;
        req.open(method, url, true);
        req.send();
    });
}