Has the user liked the post before or not using Sequelize

Question

Currently when a user likes a post, that like record gets added to my Likes table with the userId and the postId.

Now, when a user is looking at a post, I want to determi

Answer 1

You don't need to request Like once again, you got all post's likes at your hand:

for (const post of plainPosts) {
 // check if we have any like among posts' likes that is made by a certain user
 const isLiked = post.Likes.some(x => x.userId === req.user.id);
 const { Post_Images, ...postAttributes } = post;
 ...

Answer 2

You don't need to specify all the fields unless you want to override something, otherwise Sequelize can generate most of the columns for you.

const User = sequelize.define(
  'user',
  {
    name: {
      type: Sequelize.STRING,
    },
  },
  { /* options */ }
);

const Post = sequelize.define(
  'post',
  {
    title: {
      type: Sequelize.STRING,
    },
  },
  { /* options */ }
);

// the join table so you can reference it, but doesn't need any columns including primary key (unless you want to a "super join")
const Likes = sequelize.define(
  'likes',
  {}, // no columns here
  { /* options */ }
);

Creating the associations between the models will create most of the foreignKey fields automatically. Use the through keyword on the Likes relationships to make it many-to-many.

// Users can have many Posts
User.hasMany(Post);

// Posts belong to one User
Post.belongsTo(User);

// Users can like more than one Post through the `likes` join table
User.hasMany(Post, { as: 'likes', through: 'likes' });

// Posts can be liked by more than one User through the `likes` join table
Post.hasMany(User, { as: 'likes', through: 'likes' });

You don't need to store the number of likes because you can summarize it through the join table.

// Get the 'likes' count for a Post, instead of saving it on the post
const posts = await Post.findAll({
  attributes: {
    include: [
      [sequelize.fn('COUNT', sequelize.col('likes.userId')), 'likesCount'],
    ],
  },
  include: [
    {
      model: User,
      as: 'likes',
      though: 'likes',
      attributes: [],
      required: false,
    },
  ],
});

// `posts` will be an array of Post instances that have a likesCount property
posts.forEach((post) => {
  console.log(`The post ${post.title} has ${post.likesCount} likes.`);
});

For an individual (or more than one) Post you can get the list of users who liked it via the post (or use the Like model and it's relationships).

// Get the user 'likes' for a Post
const post = await Post.findByPk(postId, {
  include: [
    {
      model: User,
      as: 'likes',
      though: 'likes',
      required: false,
    },
  ],
});

post.likes.forEach((like) => {
  console.log(`The user ${like.name} has liked the post ${post.title}.`);
});