query_mutations.js

const typeDefs = gql`
  type Query {
    Posts: [Post],
  }
  type Mutation {
    addPost(title: String!, content: String!): [Post]
  }
  
  type Post {
    title: String
    content: String
  }
`;

const resolvers = {
  Query: {
    Posts: () => posts,
  },
  Mutation: {
    addPost: (obj, args) => {
        posts.push({title: args.title, content: args.content});
        return posts;
    }
  }
};

let posts = [
    {   title: 'Harry Potter',  content: 'J.K. Rowling',},
    {   title: 'Jurassic Park', content: 'Michael Crichton',},
];