简短的if-else返回Javascript错误

Question

The following JS line of code is not working as I'd expect.

When imageUrl has a value I get the following error and I expect notificationBody to be = "You received a new image message."

What am I missing here?

invalid value for the "notification.body" property. Values must be strings.

const notificationBody = (imageUrl === "" ? "You received a new image message." : messageTxt)

message payload:

const payload = {
            notification: {
              title: senderName + " sent you a message",
              body: notificationBody
            },

entire function:

exports.notifyNewMessage = functions.database.ref('/messages/{pushId}').onCreate((snap, context) => {

  const messageSnap = snap.val(); //snap.after.val();

  const fromId = messageSnap.fromId; 
  const toId = messageSnap.toId; 
  const messageTxt = messageSnap.message; 
  const imageUrl = messageSnap.imageUrl; 

  console.log('fromId: ', fromId);
  console.log('message: ', messageTxt);

  // Get the list of device notification tokens.
  const getDeviceTokensPromise = admin.database().ref('/fcmtokens/' + toId + '/registrationtokens').once('value');

  console.log('getDeviceTokensPromise', getDeviceTokensPromise);


  return admin.database().ref('/fcmtokens/' + toId + '/registrationtokens').once('value').then((userTok) => {

    const registrationTokens = Object.keys(userTok.val())

    console.log('registrationTokens', registrationTokens);


    return admin.database().ref('/users/' + fromId).once('value').then((userDoc) => {

      const user = userDoc.val(); //snap.after.val();

      const senderName = user.firstName //'Vanessa' //userDoc.firstName //get('firstName')
      console.log('senderName: ', senderName);

      const notificationBody = (imageUrl === "" ? "You received a new image message." : messageTxt)

      console.log('imageUrl: ', imageUrl);
      console.log('messageTxt: ', messageTxt);
      console.log('notificationBody: ', notificationBody);

        //build media messages notification
        const payload = {
            notification: {
              title: senderName + " sent you a message",
              body: notificationBody
            },
            data: {
              SENDER_NAME: senderName,
              SENDER_ID: fromId

            }//end data
        }//end payload

        //send message
        return admin.messaging().sendToDevice(registrationTokens, payload).then( response => {

          const stillRegisteredTokens = registrationTokens

          response.results.forEach((result, index) => {

                    const error = result.error

                    if (error) {

                        const failedRegistrationToken = registrationTokens[index]

                        console.error('blah', failedRegistrationToken, error)

                        if (error.code === 'messaging/invalid-registration-token' || error.code === 'messaging/registration-token-not-registered') {

                                const failedIndex = stillRegisteredTokens.indexOf(failedRegistrationToken)

                                if (failedIndex > -1) {
                                    stillRegisteredTokens.splice(failedIndex, 1)
                                }

                            }
                    }

                })//end forEach

                var  validTokens = {};

                stillRegisteredTokens.forEach(function(element){
                  console.log('valid token: ', element);
                  validTokens[element] = true;
                });
                //updates['registrationtokens'] = stillRegisteredTokens; ....update(updates);

                return admin.database().ref('fcmtokens/' + toId + '/registrationtokens').set(validTokens)

                // return admin.database().ref("fcmtokens/" + toId).update({
                //     //registrationTokens: stillRegisteredTokens
                // })//end update

        })//end sendToDevice


    })//end return-then

  })//end return-then

});

Answer 1

First, it looks like if imageUrl is not "" then notificationBody will be the value of messageTxt , not the "You received a new image message." string.

The javascript ternary statement works this way:

const foo = (<conditional> ? <value if conditional is True> : <value if conditional is False>)

Second, are you sure your example code is exactly the same as the code you are getting the error with? I see no reference to notification.body in your example.

Answer 2

Your ternary isn't doing what you expect, the first case is for true, the second is for false, so you could either switch around your cases, or in my solution below, switch the comparison operator to !==

What I suspect is happening in your code, because your ternary is incorrect, is that you don't have a value set for messageTxt , and so it's passing undefined into your payload as the value of body

I'd also highly suggest using JSON.stringify() around your payload if you're not doing that already.

Solution

 const senderName = 'tacocat'; const imageUrl = 'something'; const messageTxt = 4815162342 const notificationBody = ( imageUrl !== "" ? "You received a new image message." : messageTxt ) const payload = JSON.stringify({ notification: { title: senderName + " sent you a message", body: notificationBody } }) console.log(payload) 

Documentation

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator