Loop Animation With Markers - After Effects Expression by Animoplex

LoopWithMarkers.jsx

// Loop Animation With Markers - Created by Animoplex: www.animoplex.com
// Repeat a property's keyframed animation, resetting the loop at the start of every layer marker
// Based loosely on Marker Sync Expression: http://www.motionscript.com/design-guide/marker-sync.html

n = 0;
if (marker.numKeys > 0) {
    n = marker.nearestKey(time).index;
    if (marker.key(n).time > time) {
        n--;
    } // get previous marker index
}
if (n == 0) {
    value;
} else {
    m = marker.key(n); // m is target marker
    t = time - m.time; // time since target marker
    try {
        valueAtTime(key(1).time + t); // play from first keyframe
    } catch(err) {
        value;
    }
}