Uncaught TypeError: firebase.firestore()…set is not a function at HTMLButtonElement.<anonymous>

Question

I use Firebase to develop a web app. I got this error message

Uncaught TypeError: firebase.firestore(...).collection(...).orderBy(...).limit(...).set is not a function
    at HTMLButtonElement.<anonymous> (main.js:152)

because of this code.

firebase.firestore().collection('script').orderBy('timestamp','desc').limit(1).set({
    finaltext: resultText.value,
    name: firebase.auth().currentUser.displayName,
    uid: firebase.auth().currentUser.uid
  },{merge: true}).catch(function(error){
    console.error('Error writing new message to Firestore', error);
  });

I searched the Internet, but couldn't find why this error message occurred. Could you give me any advice, please?

Answer 1

The method limit returns a value of type Query :

limit

limit ( limit: number ): Query < T >

Creates and returns a new Query that only returns the first matching documents.

https://firebase.google.com/docs/reference/js/firebase.firestore.Query#limit

Therefore both orderBy and limit are used when you want to retrieve data. If you want to add data to the database then just do the following:

firebase.firestore().collection('script').set({
    finaltext: resultText.value,
    name: firebase.auth().currentUser.displayName,
    uid: firebase.auth().currentUser.uid
  },{merge: true}).catch(function(error){
    console.error('Error writing new message to Firestore', error);
  });

Answer 2

You need to first fetch the desired document, with get() , before writing the new field(s) with set() (with merge option) or update() .

firebase.firestore().collection('script').orderBy('timestamp','desc').limit(1).get()
.then(querySnapshot => {
    if (!querySnapshot.empty) {
        //We are sure the document exists, we can then use update()
        return querySnapshot.docs[0].ref.update({
          finaltext: resultText.value,
          name: firebase.auth().currentUser.displayName,
          uid: firebase.auth().currentUser.uid
        });
    } else {
       throw new Error("No document");
    }
})
.catch(error => {
    console.log("Error:", error);
});

Note that the get() method returns a QuerySnapshot , so you need to do querySnapshot.docs[0] to get the DocumentSnapshot corresponding to the unique doc returned by the query.