Motion Design - Loop Script

try{
timeStart = thisProperty.key(1).time;
duration = thisProperty.key(thisProperty.numKeys).time-timeStart;
pingPong = false; //change to true value if you want to loop animationn back & forth
quant=Math.floor((time-timeStart)/duration);
  if(quant<0) quant = 0
  if(quant%2 == 1 && pingPong == true){   t = 2*timeStart+ (quant+1)*duration - time;
}
else{
  t = time-quant*duration;
}
}
catch(err){
  t = time;
}
thisProperty.valueAtTime(t)