in database/read-and-write.js [108:124]
function toggleStar(postRef, uid) {
postRef.transaction((post) => {
if (post) {
if (post.stars && post.stars[uid]) {
post.starCount--;
post.stars[uid] = null;
} else {
post.starCount++;
if (!post.stars) {
post.stars = {};
}
post.stars[uid] = true;
}
}
return post;
});
}