javascript承诺使用firebase云函数不会对通知进行嵌套和返回错误

Question

我正在尝试使用firebase函数进行通知，但我的index.js文件有问题。我需要一点帮助来解决这个问题。如何避免嵌套承诺和返回错误？谢谢

const functions = require('firebase-functions');
const admin= require('firebase-admin');
admin.initializeApp();
let firebaseConfig = JSON.parse(process.env.FIREBASE_CONFIG);
exports.sendNotification = functions.database.ref('/Notifications/ {user_id}/{notification_id}').onWrite((change,context) => {
const user_id = context.params.user_id; 
const notification= context.params.notification;
console.log('We have a notification to send to ',user_id);
if(!change.after.val()){
return console.log('A Notification has beed deleted from the database : ' , notification_id);
}
const deviceToken = admin.database().ref(`/Users/${user_id}/device_token`).once('value');
return deviceToken.then(result =>{
const token_id = result.val();
const payload = {
notification: {
title : "Friend Request",
body : "You have received a new Friend Request",
icon : "default"
}
};
return admin.messaging().sendToDevice(token_id, payload).then(response =>{
console.log("This was the notification Feature");
});
});

以下是我的错误：

31:21  warning  Avoid nesting promises                      promise/no-nesting
31:76  error    Each then() should return a value or throw  promise/always-return
✖ 2 problems (1 error, 1 warning)
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.
npm ERR! A complete log of this run can be found in:
npm ERR!     C:UsersfurkanAppDataRoamingnpm-cache_logs2018-05-27T20_21_53_984Z-debug.log
Error: functions predeploy error: Command terminated with non-zero exit code1
Having trouble? Try firebase deploy --help

Answer 1

尝试返回sendToDevice返回的promise，而不是像回调一样嵌套它，这样它就可以被链接在外部而不是内部。它还希望您从每个then显式返回一个值，这样您就可以从最后一个return为null或未定义来抑制警告：

return deviceToken.then(result =>{
const token_id = result.val();
const payload = {
notification: {
title : "Friend Request",
body : "You have received a new Friend Request",
icon : "default"
}
};
return admin.messaging().sendToDevice(token_id, payload);
}).then(response => {
console.log("This was the notification Feature");
return undefined;
});