Question

The current problem now is i changed the function i got from the awnser but the previous one doesn’t work.

function getPrev(currPhotoId) {
    var i = currPhotoId - 1;
    i %= album.length;
    while ( album[i].disabled ) {
        i--;
        i %= album.length;
    }
    return i;
}

The output works as long it is above 0

TypeError: album[i] is undefined
undefined = "0"   
while ( album[i].disabled ) 

Answer 1

The following logic is pretty simple. The trick is to just keep iterating until you find one that is not disabled, using modulus (%) to perform the loop-around when you hit the end.

function getNext() {
    var i = this.currPhotoId + 1;
    i %= this.album.length;
    while ( this.album[i].disabled ) {
        i++;
        i %= this.album.length;
    }
    return this.album[i];
}

function getPrev() {
    var i = this.currPhotoId - 1;
    i %= this.album.length;
    while ( this.album[i].disabled ) {
        i--;
        i %= this.album.length;
    }
    return this.album[i];
}

Just make sure there’s at least one that is enabled or this will loop infinitely. 🙂