How to change value in After Effects when passing marker

Question

I am running into an issue where I want to change the value of my slider controller (just adding 1) each time it passes by a marker. This is my current code

if (marker.numKeys > 0) { value = marker.nearestKey(time).index; }

However, the issue I am running into is that midway between markers it changes value.

Answer 1

You just need to check if the nearest marker is in the past or the future. If it's in the future, just subtract 1 from its index. This avoids the use of a loop.

if (marker.numKeys > 0) {
    nearestMarker = marker.nearestKey(time);
    if (nearestMarker.time > time){
        nearestMarker.index - 1;
    } else {
        nearestMarker.index;
    }
}

You can shorten this using a ternary operator—at the cost of readability—to

if (marker.numKeys > 0) {
    nearestMarker = marker.nearestKey(time);
    nearestMarker.index - ((nearestMarker.time > time)? 1 : 0 )
}

Answer 2

marker.nearestKey picks the closest marker - even if it is in the future.

A simple solution would be to iterate over the markers with a for loop instead:

if (marker.numKeys > 0) {
    let i;
    for (i = 0; i < marker.numKeys; i++) { // For every marker we have, add 1 to i
        if (marker.key(i+1).time > time)   // If the marker is past current time,
            break;                         // stop the loop
    }
    i; // Return i value
}