SOURCE

function newAjax(url) {
    return new Promise((resolve, reject) => {
        let xhr = new XMLHttpRequest();
        xhr.open("GET", url, true)
        xhr.onreadystatechange = function () {
            if (this.readyState !== 4) {
                return;
            }
            if (this.status === 200) {
                resolve(this.response)
            } else {
                reject(new Error(this.statusText))
            }
        }
        xhr.onerror = function () {
            reject(new Error(this.statusText))
        }
        xhr.responseType = "json";
        xhr.setRequestHeader("Accept", "application/json")
        xhr.send(null);
    })
}