hot-update/packages/update-manager/templates/pre_main.js

window.beforeBoot = function () {
    cc.log("游戏正在启动中.")
    if (window.remoteUrl) {
        const settings = window._CCSettings;
        settings.server = window.remoteUrl;
        cc.log("远程资源地址:", settings.server);
    }
    let url = window.updateUrl || false;
    if (!url) {
        cc.log("未配置版本更新地址,跳过更新.")
        window.boot();
        return;
    }

    // 请求缓存信息,判断是否需要更新.
    let assetStr = window.localStorage.getItem('version_data');
    if (!assetStr) {
        window.boot();
    } else {
        let asset = JSON.parse(assetStr);
        window.mergeVersion(asset);
        window.boot();
    }
    // 游戏启动后再请求更新,避免影响启动速度.
    url += `?_t=${Math.random()}`;
    cc.log("请求更新地址:", url);
    get(url, function (err, asset) {
        if (err || !asset) {
            return;
        }
        window.localStorage.setItem('version_data', asset);
    });
};
window.mergeVersion = function (updateInfo) {
    const settings = window._CCSettings;
    const bundleVers = updateInfo.bundles;
    if (bundleVers) {
        for (let b in bundleVers) {
            if (bundleVers[b] != settings.bundleVers[b]) {
                // 配置中的bundleVer版本不一致,则添加到remote列表中去,以供远程加载.
                if (settings.remoteBundles.indexOf(b) < 0) {
                    settings.remoteBundles.push(b);
                }
            }
        }
        settings.bundleVers = bundleVers;
    }
    return;
}

// ajax 请求.
function get(url, cb) {
    const ajax = new XMLHttpRequest();
    ajax.open("get", url, true);
    ajax.setRequestHeader("Content-Type", "application/json;charset=utf-8");
    ajax.onreadystatechange = function () {
        if (ajax.readyState == 4) {
            if (ajax.status == 200) {
                // var response = JSON.parse(ajax.responseText)
                cb && cb(null, ajax.responseText);
                return;
            } else {
                cb && cb("request error!");
            }
        }
    }
    ajax.send(null);
}