尽管条件为真，但 Array.filter() 返回空数组

Question

I am trying to use filter to create a new array coming from firebase-firestore

this is the filter function- when console loging the result of myTweet.userId === firebase.auth().currentUser.uid it returns true.

  isEqualToMyTweets = (myTweet) => {
        console.log(myTweet.userId)
        console.log(firebase.auth().currentUser.uid)
        console.log(myTweet.userId === firebase.auth().currentUser.uid)
        return myTweet.userID == firebase.auth().currentUser.uid;
    }

yet when calling the function it returns an empty array:

    onListenForTweets() {
        this.unsubscribe = firebase.firestore()
            .collection('tweets')
            .orderBy('date', 'desc')
            .limit(this.state.limit)
            .onSnapshot((snap) => {
                const tweets = snap.docs.map(docs =>
                    ({ ...docs.data(), id: docs.id })
                   
                );
                this.setState({ tweets })

                let myTweets = tweets.filter(this.isEqualToMyTweets);               
            });
    }

the reason I'm doing this is that i want to introduce a condition and accordingly present the tweets of a certain user.

this is the components code:

    constructor(props) {
        super(props);
        this.state = {
            tweets: [],
            loading: false,
            profile: "",
            interval: null,
            limit: 10,
        };
        this.myTweets = []
    }

    componentDidMount() {
        this.onListenForTweets()
    }

    isEqualToMyTweets = (myTweet) => {
        console.log(myTweet.userId)
        console.log(firebase.auth().currentUser.uid)
        console.log(myTweet.userId === firebase.auth().currentUser.uid)
        return myTweet.userID == firebase.auth().currentUser.uid;
    }

    onListenForTweets() {
        this.unsubscribe = firebase.firestore()
            .collection('tweets')
            .orderBy('date', 'desc')
            .limit(this.state.limit)
            .onSnapshot((snap) => {
                const tweets = snap.docs.map(docs =>
                    ({ ...docs.data(), id: docs.id })
                   
                );
                this.setState({ tweets })
                let myTweets = tweets.filter(this.isEqualToMyTweets);
                console.log(myTweets)
            });
    }

    async handleOnNewTweet(newTweet) {
        await firebase.firestore()
            .collection('tweets')
            .add(newTweet)
    }

    componentWillUnmount() {
        this.unsubscribe();
    }

this is an example of the console.log

TweetRoom.jsx:38 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:39 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:40 true
TweetRoom.jsx:38 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:39 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:40 true
TweetRoom.jsx:38 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:39 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:40 true
TweetRoom.jsx:38 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:39 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:40 true
TweetRoom.jsx:38 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:39 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:40 true
TweetRoom.jsx:38 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:39 c1btNa39vZe3ptPfuYUn2chUsAn1
TweetRoom.jsx:40 true
TweetRoom.jsx:56 []length: 0__proto__: Array(0)

Answer 1

Posting this as a community wiki as this solution was pointed out in the comments to this thread by @PeterSeliger.

The issue is being caused by the final call of your isEqualToMyTweets function where you are calling myTweet.userID instead myTweet.userId without the final capital letter, thus the comparison always fails and you get an entirely empty array as a result.

So changing it to myTweet.userId will solve the issue.