承诺在向服务器发送值后返回undefined

Question

我刚刚开始在javascript中使用promise函数，我确实喜欢它，但我遇到了一个问题。

我从promise对象获取一个值，然后在异步promise函数中将响应发送回服务器。当我将值发送回服务器，并尝试查看值是什么时，它返回undefined。

var xhr = new XMLHttpRequest();
    function createFirstChannel(method, rippleApi) {
        return new Promise(function (resolve, reject) {
            xhr.open(method, url, true);
            xhr.setRequestHeader("Content-Type", "application/json");
            xhr.onload = function () {
                if (xhr.readyState == 4 ) {
                    var hashValue = resolve(JSON.parse(xhr.responseText));
                }
                else {
                    reject({
                        status: this.status,
                        statusText: xhr.statusText
                    });
                }
            };
            xhr.onerror = function () {
                reject({
                    status: this.status,
                    statusText: xhr.statusText
                });
            };
             xhr.send(json);
        });
    }

从我在下一个promise函数中使用的第一个函数返回一个值

    async function createChannel(method, url) {
        var datums = await createFirstChannel(method, url);
            //method to return hash value from json request
             for (var key in datums) {
        var tx_json = datums[key]['json'];
        datums = (json['hash']);
        console.log(datums);
    }
            //creating the json request to send back out again using POST METHOD
            var channel= {
                "method": "tx",
                "par": [{
                    "transaction": datums
                }]
            }
            var jsonPayee = JSON.stringify(channel);
            xhr.open(method, url, true);
            xhr.setRequestHeader("Content-Type", "application/json");
            xhr.onload = function () {
                if (xhr.readyState == 4) {
                    users = JSON.parse(xhr.responseText);
                }
            };
          xhr.send(jsonPayee);
        return users;
        }
        createChannel(method, url).then(datums => {
            console.log(datums);
        }).catch(function (err) {
            console.error('Sorry There Was An Error!', err.statusText);
        });

i get "undefined" response at console.log. is there any way to resolve this error? Thanks for the help