var url = _spPageContextInfo.webAbsoluteUrl + "/_api/web/currentuser";
    $.ajax({
        url: url,
        headers: {
            Accept: "application/json;odata=verbose"
        },
        async: false,
        success: function (data) {
            var items = data.d; // Data will have user object
            console.log(items);
        },
        eror: function (data) {
            alert("An error occurred. Please try again.");
        }
    });