src/loaders/file.js

class File {
    static load(url) {
        return new Promise((resolve, reject) => {
            const req = new XMLHttpRequest();
            req.open('GET', url);
            req.onload = () => {
                if (req.status === 200) {
                    resolve(req.response);
                } else {
                    reject(Error(req.statusText));
                }
            };

            req.onerror = () => {
                reject(Error('Network Error'));
            };

            req.send();
        });
    }
}

export default File;