Promise based XHR Wrapper

_http.js

let _Http = obj => {
    return new Promise((resolve, reject) => {
        let xhr = new XMLHttpRequest();
        xhr.open(obj.method || "GET", obj.url);
        if (obj.headers) {
            Object.keys(obj.headers).forEach(key => {
                xhr.setRequestHeader(key, obj.headers[key]);
            });
        }
        xhr.onload = () => {
            if (xhr.status >= 200 && xhr.status < 300) {
                resolve(JSON.parse(xhr.response));
            } else {
                reject(xhr.statusText);
            }
        };
        xhr.onerror = () => reject(xhr.statusText);
        xhr.send(JSON.stringify(obj.body));
    });
};

    //Guildelines to use
    /*
    _http({
         method: 'POST',   //GET by default
         url: 'data.json',
         body: JSON.stringify(payload)
         headers: {
            'my-custom-header': 'value'
         }
     })
      
      */