AfterEffects trolly loop for accumulating values over each iteration

ae-trolly-loop.tsx

loopDur = key(numKeys).time - key(1).time;

// only run while this layer is active
if (time < inPoint) {
    // before layer starts → hold first keyframe
    key(1).value;
} else if (time > outPoint) {
    // after layer ends → hold the final accumulated value at outPoint
    tEnd = outPoint - key(1).time;
    loopCountEnd = Math.floor(tEnd / loopDur);
    tInLoopEnd = (tEnd % loopDur) + key(1).time;

    loopValueEnd = valueAtTime(tInLoopEnd);
    offsetEnd = (key(numKeys).value - key(1).value) * loopCountEnd;

    loopValueEnd + offsetEnd;
} else {
    // active portion → normal accumulation
    t = time - key(1).time;
    loopCount = Math.floor(t / loopDur);
    tInLoop = (t % loopDur) + key(1).time;

    loopValue = valueAtTime(tInLoop);
    offset = (key(numKeys).value - key(1).value) * loopCount;

    loopValue + offset;
}