update_post.js

updatePost(parent,args, ctx, info){
        const post = ctx.posts.find((post) => post.id === args.id)
        const originalPost = {...post} //spread operator
        if (!post) {
            throw new Error('Post not found')
        }

        if (typeof args.body === 'string') {
            post.body = args.body
        }

        if (typeof args.published === 'boolean') {
            post.published = args.published
            pubsub.publish('post', {
                post:{
                    mutation: 'UPDATED',
                    data: post
                }
            })  
        }

        

        return post
    },