Finding an index in an array of objects with 3 possible outcomes

Question

currentUserPosts will have a post object with an id that either matches a tempId, an Id, or nothing.

If there's a tempId match there won't be an id match and vice versa.

This code works but there's something about it I don't like. How can it be refactored?

let postIndex;
postIndex = currentUserPosts.findIndex(post => post.id === upsertParams.tempId);
if (postIndex === -1) {
 postIndex = currentUserPosts.findIndex(post => post.id === upsertParams.id);
}
if (postIndex === -1) {
 currentUserPosts.push(upsertParams);
} else {
 currentUserPosts[postIndex] = upsertParams;
}

Complete function:

const upsertIntoApolloCache = (upsertParams) => {
 try {
 const data = client.readQuery({
 query: USER_POSTS_QUERY,
 });
 const currentUserPosts = data.currentUser.posts;
 const postIndex = currentUserPosts.findIndex(
 post => post.id === upsertParams.tempId || post.id === upsertParams.id
 );
 if (postIndex === -1) {
 currentUserPosts.push(upsertParams);
 } else {
 currentUserPosts[postIndex] = upsertParams;
 }
 client.writeQuery({
 query: USER_POSTS_QUERY,
 data,
 });
 } catch (error) {
 console.log('!!ERROR in upsertIntoApolloCache!!', error);
 }
};

Answer 1

You can group the two conditions for finding into a single || condition, since the post.id can match only one of tempId or id.

let postIndex = currentUserPosts.findIndex(post => {
 return post.id === upsertParams.id || post.id === upsertParams.tempId
});
if (postIndex === -1) {
 currentUserPosts.push(upsertParams);
} else {
 currentUserPosts[postIndex] = upsertParams;
}

You could, if possible, also change the currentUserPosts from array to a dictionary mapping your post.id to the post itself. This entirely depends on your further usage of the currentUserPosts across application.

---

Based on updated question content:

let currentUserPosts = {}
for (let post of data.currentUser.posts) {
 currentUserPosts[post.id] = post
}

This way, you'd only have to check against id using the in operation:

let newId = upsertParams.id || upsertParams.tempId
if (newId in currentUserPosts)
 // do unspeakable things

• Gerrit0: Looks to me like you are missing a return in your findIndex method.
• GollyJer: Ha!! That was an easy one. Thanks @hjpotter92! Regarding your second suggestion. Don't completely understand what you're getting at. I'll update my questions with the full function so you can see. It probably doesn't matter because I don't have control of the structure. It's a cache object provided by Apollo.