Javascript ReferenceError:未定义上下文

我正在尝试使用node.js和firebase函数创建sendNotification函数，但不幸的是，我目前被卡住了。我从未收到发件人的通知，当我查看Firebase函数日志时，我看到一个错误，上面写着

ReferenceError: context is not defined
at exports.sendNotification.functions.database.ref.onWrite.event (/user_code/index.js:9:32)
at Object.<anonymous> (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:112:27)
at next (native)
at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:28:71
at __awaiter (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:24:12)
at cloudFunction (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:82:36)
at /var/tmp/worker/worker.js:700:26
at process._tickDomainCallback (internal/process/next_tick.js:135:7)

我不知道错误在哪里有人能告诉我错误在哪里，我如何解决它吗？

将其更改为：

exports.sendNotification = functions.database.ref('notifications/{user_id}').onWrite((change,context) => {

const user_id = context.params.user_id;

});

onWrite

有两个参数

change

和

context

。您可以使用

context

访问通配符示例

user\u id

更多信息请点击此处：

---

在@PeterHaddad的帮助下，我设法解决了自己的问题。我阅读了他发布的链接，并更改了一些代码。给你

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.sendNotification = functions.database.ref('notifications/{user_id}').onWrite((change, context) => {

const user_id = context.params.user_id;
const notification_id = context.params.notification_id;

console.log('We have notification from: ', user_id);

if (!change.after.val()) {
    return console.log('A Notification has been deleted from the database: ', notification_id);
}

const fromUser = admin.database().ref(`/Users/${user_id}/device_token`).once('value');

return fromUser.then(result => {

    const token_id = result.val();

    const payload = {
        notification: {
            title: "Friend Request",
            body: "You've received a Friend Request",
            icon: "default"
        }
    };

    return admin.messaging().sendToDevice(token_id , payload).then(response => {

        console.log('This was the notification feature');

    });

});

});

---

这正是错误所说的-您在使用它之前从未定义过

上下文

。？好的，那么我如何在这里定义上下文？我不知道，这是您的应用程序-当您访问它的

.params.user\u id

时，您似乎在想什么。找出该对象是什么，并在使用它之前将其分配给

上下文
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.sendNotification = functions.database.ref('notifications/{user_id}').onWrite((change, context) => {

const user_id = context.params.user_id;
const notification_id = context.params.notification_id;

console.log('We have notification from: ', user_id);

if (!change.after.val()) {
    return console.log('A Notification has been deleted from the database: ', notification_id);
}

const fromUser = admin.database().ref(`/Users/${user_id}/device_token`).once('value');

return fromUser.then(result => {

    const token_id = result.val();

    const payload = {
        notification: {
            title: "Friend Request",
            body: "You've received a Friend Request",
            icon: "default"
        }
    };

    return admin.messaging().sendToDevice(token_id , payload).then(response => {

        console.log('This was the notification feature');

    });

});

});