Fetching data using limitoLast returns null using endAt()

Question

I wanted to implement infinite scroll to load more data in my app. I wanted to fetch the data from latest to oldest i.e from bottom to top , so I have used limiToLast()

I have followed Implementing Infinite Scrolling with Firebase? to achieve this functionality.

Here is my query function

var lastKey = '';
var myData = [];

async fetchData(){
    try{
        var snap = await firebase.database().ref(category).orderByKey().endAt(lastKey).limitToLast(5).once('value');
        console.log(snap);
        snap.forEach(childSnap => {
            myData.push(childSnap.val();
            lastKey = childSnap.key;
        });
    }catch(err){
        //handle errors
    }
}

But the snap is null if I console.log it. what am I doing wrong? I want to fetch 5 items at a time from the bottom if I use the same code using startAt() and limitToFirst() to fetch 5 items at a time it works fine:

var lastKey = '';
var myData = [];

async fetchData(){
    try{
        var snap = await firebase.database().ref(category).orderByKey().startAt(lastKey).limitToFirst(5).once('value');
        snap.forEach(childSnap => {
            myData.push(childSnap.val();
            lastKey = childSnap.key;
        });
    }catch(err){
        //handle errors
    }
}

your lastKey is empty when you do endAt, so i think it will stop even before even hitting the first node. — davidchoo12, Oct 09 '17 at 09:21
startAt works by starting the search from an empty string, so it will start from the first element — davidchoo12, Oct 09 '17 at 09:34
Please edit your question to include the `console.log()` statement, since the behavior depends on *where* you log. — Frank van Puffelen, Oct 09 '17 at 14:51
I have edited the question and added the console.log statement — boomboxboy, Oct 10 '17 at 08:10

Fetching data using limitoLast returns null using endAt()

0 Answers0