IndexedDB retrieving all objects and adding them to an array, cursor is null

Question

I am trying make a function that returns an array of all the objects in an object store. This is the JavaScript code I currently have:

function readAllSessions() {
    var output = [];
    database.transaction("practiceSessions").objectStore("practiceSessions").openCursor().onsuccess = function (e) {
        var cursor = e.target.result;
        if (cursor) {
            output.push(cursor.value);
            cursor.continue();
        }
    }
    return output;
}

This returns an empty array. I found that the cursor object is null, but I can't see why, since there are 3 objects in the object store.

Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — mpm, Sep 23 '18 at 21:57

score 3 · Answer 1 · answered Sep 23 '18 at 22:03

you can't return anything from a asynchronous call without a callback or a promise, here is a the function implemented with a callback.

function readAllSessions(callback) {
    var output = [];
    database.transaction("practiceSessions").objectStore("practiceSessions").openCursor().onsuccess = function (e) {
        var cursor = e.target.result;
        if (cursor) {
            output.push(cursor.value);
            cursor.continue();
        }else{
          callback(output)
        }
    }
}


readAllSessions(function(output){
   // use output here.
})

for future reference, please read this question and its answers :

How do I return the response from an asynchronous call?

This process is the very essence of working with Web API in the browser.

IndexedDB retrieving all objects and adding them to an array, cursor is null

1 Answers1