Node.js Firebase云函数表示不可访问，每个then（）都应返回一个值或抛出promise/always return Firebase云函数的Javascript代码，给出了为推送通知编写的错误 index.js

当运行firebase部署命令时，出现如下错误。如果有人能支持我，我将不胜感激

错误 error Each then（）应返回值或抛出promise/always return 错误不可访问代码不可访问 error Each then（）应返回值或抛出promise/always return

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! functions@ lint: `eslint .`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the functions@ lint script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.      

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错误是说您应该从传递给任何then（）方法的回调返回一个值。代码中有两个then（）方法。如果您没有要发送到承诺链中的下一项工作的内容，只需在函数末尾返回null即可

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不过，代码中还有一个更大的问题。在函数的顶层有两个

return

语句，一个接一个。这几乎肯定会导致另一个错误，或者至少无法达到您的预期。（您必须只返回一个承诺，在所有工作完成后解决。）

道格感谢您的评论。然后我改变了密码。现在它已部署完毕，没有任何错误。但调用该方法后，firebase函数控制台中会出现错误。（调用该方法意味着使用android应用程序添加新通知） 在有效负载中，没有令牌：deviceToken部分也不工作

'use strict'


//Install functions and admin sdks'
const functions = require('firebase-functions');
const admin =require('firebase-admin');
var FCM = require('fcm-push');
admin.initializeApp();


var serverKey = 'MY_SERVER_KEY_HERE';
var fcm = new FCM(serverKey);



exports.sendNotification = functions.database.ref('/notifications/{user_id}/{notification_id}').onWrite((change, context) => {
    //onwrite will run if data changed
    const user_id = context.params.user_id;
    const notification = context.params.notification;
console.log('user : '+user_id)
console.log('notification : '+notification)
    // If exit the function.
    if (!change.after.val()) {
      return console.log('User ', user_id, 'notification', notification);
    }

// Only edit data when it is first created.
      if (change.before.exists()) {
        return null;
      }
      // Exit when the data is deleted.
      if (!change.after.exists()) {
        return null;
      }

    const deviceToken = admin.database().ref(`/Users/${user_id}/device_token`).once('value');
    console.log("Dev TOken : "+deviceToken);
    return admin.database().ref(`/Users/${user_id}/device_token`).once('value').then(result => {


        const payload = {
            notification:{
                title:"Friend Request",
                body:"You have recieved a new friend request",
            },
            tokens:deviceToken
        };

        return admin.messaging().send(payload).then(response =>{
            return console.log('This is the notify feature');
        }).catch(err => {
            return console.log('Error getting documents', err);
        });
    })

});

输出：-

---

如果有错误，有人能纠正代码吗？

我希望它能正常工作，您应该像这样返回

return console.log('This is the notify feature');

---

谢谢大家。我修好了

'use strict'

//Install functions and admin sdks'
const functions = require('firebase-functions');
const admin =require('firebase-admin');
admin.initializeApp();

exports.sendNotification = functions.database.ref('/notifications/{user_id}/{notification_id}').onWrite((change, context) => {
    //onwrite will run if data changed
    const user_id = context.params.user_id;
    //const from = context.params.from;
    const notification_id = context.params.notification_id;
    console.log('user : '+user_id);
    console.log('notification_id : '+notification_id);
    //console.log('notification : '+notification)
    //console.log('from : '+from)
    // If exit the function.
    if (!change.after.val()) {
      return console.log('Sender ', user_id, 'From', from);
    }

// Only edit data when it is first created.
      if (change.before.exists()) {
        return null;
      }
      // Exit when the data is deleted.
      if (!change.after.exists()) {
        return null;
      }

    // if (context.params === null) {
    //     return console.log("Notification Has Been Deleted");
    // }

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

    return getDeviceTokensPromise.then(result => {
      const payload = {
        notification: {
          title: 'You have a new follower!',
          body: `is now following you.`,
          icon: 'default'
        }
      };

      return admin.messaging().sendToDevice(result.val(), payload);

    }).then(res => {
      return console.log(JSON.stringify(res));
    });  

});

---

对于云函数，如果其https触发器，则必须向用户返回响应；如果任何其他类型的触发器，则必须返回承诺。只是

返回承诺。解决（“完成”）我已尝试返回null，但对我无效

'use strict'

//Install functions and admin sdks'
const functions = require('firebase-functions');
const admin =require('firebase-admin');
admin.initializeApp();

exports.sendNotification = functions.database.ref('/notifications/{user_id}/{notification_id}').onWrite((change, context) => {
    //onwrite will run if data changed
    const user_id = context.params.user_id;
    //const from = context.params.from;
    const notification_id = context.params.notification_id;
    console.log('user : '+user_id);
    console.log('notification_id : '+notification_id);
    //console.log('notification : '+notification)
    //console.log('from : '+from)
    // If exit the function.
    if (!change.after.val()) {
      return console.log('Sender ', user_id, 'From', from);
    }

// Only edit data when it is first created.
      if (change.before.exists()) {
        return null;
      }
      // Exit when the data is deleted.
      if (!change.after.exists()) {
        return null;
      }

    // if (context.params === null) {
    //     return console.log("Notification Has Been Deleted");
    // }

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

    return getDeviceTokensPromise.then(result => {
      const payload = {
        notification: {
          title: 'You have a new follower!',
          body: `is now following you.`,
          icon: 'default'
        }
      };

      return admin.messaging().sendToDevice(result.val(), payload);

    }).then(res => {
      return console.log(JSON.stringify(res));
    });  

});