Sorry for troubling but when i run code like below it returns an error and after stopping debug it only applies ease to keys of first property.
var keyedProps = getPropsWithKeys(app.project.activeItem.layers[1]);
for (var i = 0; i < keyedProps.length; i++) {
var curProp = keyedProps[i];
var numKeys = curProp.numKeys;
for(var j = 0; j < numKeys; j++){
// do your custom easing HERE with curKey
var curKeyIndex = j+1;
var easeIn = new KeyframeEase(0.5, 50);
var easeOut = new KeyframeEase(0.75, 85);
curProp.setTemporalEaseAtKey(curKeyIndex, [easeIn], [easeOut]);
}
}