onMessage问题

Question

我正在学习Firebase并遇到问题：我无法发送通知。我尝试使用onMessage，但是什么也没有发生。

var message = {
    content_available: false,

    notification: {
        title: "My first Push",
        body: "My first Push",
    },
    to: token
};
global.admin.messaging().onMessage(function(message) {

        const notificationTitle = message.notification.title;
        if (!("Notification" in window)) {
            console.log("This browser does not support system   notifications");
        } else if (Notification.permission === "granted") {
            var notification = new Notification(notificationTitle, message.notification);
            notification.onclick = function(event) {
                event.preventDefault(); // prevent the browser from focusing the Notification's tab
                window.open(event.notification.click_action, '_blank');
                notification.close();
            }
        }
        console.log('Message received. ', message);
    })
    .then((response) => {
        console.log("Sucsessfully sent message:", response);
        console.log(response.results[0].error);
    })
    .catch((error) => {
        console.log("Error sending message:", error);
    })