denormalizing_data.js

// denormalizing data (client side "join")

const users = [
  { userId: 101, name: "Rahim" },
  { userId: 102, name: "Karim" },
  { userId: 103, name: "Amina" },
  { userId: 104, name: "Nusrat" },
  { userId: 105, name: "Sakib" },
  { userId: 106, name: "Tanvir" },
  { userId: 107, name: "Hasan" },
  { userId: 108, name: "Mim" },
  { userId: 109, name: "Jahid" },
  { userId: 110, name: "Arif" },
];

const posts = [
  { id: 1, userId: 101, title: "Learn JavaScript Basics" },
  { id: 2, userId: 102, title: "Understanding ES6 Features" },
  { id: 3, userId: 103, title: "Intro to React" },
  { id: 4, userId: 101, title: "Advanced React Hooks" },
  { id: 5, userId: 104, title: "CSS Flexbox Guide" },
  { id: 6, userId: 102, title: "Mastering CSS Grid" },
  { id: 7, userId: 105, title: "Node.js for Beginners" },
  { id: 8, userId: 103, title: "Express.js Crash Course" },
  { id: 9, userId: 101, title: "MongoDB Basics" },
  { id: 10, userId: 104, title: "Full Stack Development Guide" },
];

// create hash table of posts
const postByUserId = posts.reduce((table, post) => {
  const { userId } = post;

  if (!table[userId]) {
    table[userId] = [];
  }
  table[userId].push(post);
  return table;
}, {});
console.log(postByUserId);

const userWithPost = users.map((user) => {
  return {
    ...user,
    post: postByUserId[user.userId] || [],
  };
});
// console.log(postByUserId);
console.log(JSON.stringify(userWithPost));