Resolver code for PostOps

resolver.js

const voteHandler = (postId, updown) => {
    return new Promise((resolve, reject) => {
        const post = posts.find(p => p.id === postId);
        if (!post) {
            reject(`Couldn't find post with id ${postId}`);
        }
        post.votes += updown;
        resolve(post);
    })
};

const PostOps =
    ({
        upvote: ({
            postId
        }) => voteHandler(postId, 1),
        downvote: ({
            postId
        }) => voteHandler(postId, -1)
    });