[JavaScript知识库]javascript 里的Promise

function SendRequest(method, url, data, bearerToken) {
    return new Promise(function (resolve, reject) {
        var xhr = new XMLHttpRequest();
        xhr.withCredentials = true;

        xhr.addEventListener("readystatechange", function () {
            if (this.readyState === 4) {
                console.log('readyState');
                console.log(this.responseText);
            }
        });

        xhr.open(method, rootPath + url);
        xhr.setRequestHeader("Content-Type", "application/json");
        xhr.setRequestHeader("cache-control", "no-cache");
        if (typeof (bearerToken) != 'undefined') {
            xhr.setRequestHeader("Authorization", "Bearer " + bearerToken);
        }

        xhr.onload = function () {
            if (xhr.status == 200) {
                resolve(xhr.response);
            }
            else {
                reject(Error(xhr.statusText));
            }
        };

        xhr.onerror = function () {
            reject(Error("Network Error"));
        };

        if (typeof (data) != 'undefined') {
            xhr.send(JSON.stringify(data));
        } else{
            xhr.send();
        }
    });
}

为了异步执行，先定义个Promise

var token = new Token();

    token.load();
    token.requestToken('zhaoma', '1029824zzZ').then((data) => {
        var resp = JSON.parse(data);
        console.log('request token');
        console.log(resp);

        token.setToken(resp.token);
        token.setExpire(resp.expireTime);

        token.save();
    });

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