run182

var wasAuth = new Promise(
    function (resolve, reject) {
        fetch('ajax.php')
            .then(function(response) {
                return response.json();
            })
            .then(function(res) {
                resolve("Auth == true");
                // OR
                reject(new Error("Auth == false"));
            })
            .catch(alert);
       }
);
var sell = function () {
   wasAuth
         .then(function (fulfilled) {
             console.log(fulfilled); // Auth == true
         })
         .catch(function(error) {
            console.log(error.message); // Auth == false
        });
};
sell();