// const remainingEffects = effectHolders.filter(holder => !holder.effect.isExpired());

const remainingEffects = [];

for (let i=0; i<9; i++) {
    if (!effectHolders[i].isExpires()) {
        remainingEffects.push(effectHolders[i]);
    }
}

for (let i=0; i<9; i++) {
    if (i < remainingEffects.length) {
        effectHolders[i].copyFrom(remainingEffects[i]);
    } else if (effectHolders[i]) { // Not sure what this conditional should be
        effectHolders[i].erase();
    }
}