I am writing a webapp for practice. I have several sequelize models, and querying the db through them so far has been no issue. However, when I tried to use a junction table to return what would be a simple join in SQL, I ran into an issue.

See the query:
Goal: Get every chat a user is a member of.

const models = require('../db/models');
...
...
(inside an api endpoint)
        const userChats = await models.User.findOne({ 
            where: { id: req.user.id },
            include: [
                {
                    model: models.Chat,
                    through: models.User_Chat
                }
            ]
        });

When I try this, I get the following error:

C:...mypath...node_modulessequelizelibdialectsabstractquery-generator.js:1376
    const throughTable = through.model.getTableName();
                                       ^

TypeError: Cannot read properties of undefined (reading 'getTableName')

For reference, here are the relevant models and the initialization of those models:

Chat model:

const { sq } = require("../config/db");
const { DataTypes } = require('sequelize');


const Chat = sq.define('Chat', {
    id: {
        type: DataTypes.UUID,
        primaryKey: true,
        defaultValue: DataTypes.UUIDV4, // Automatically generate UUID
        allowNull: false
    },
    name: {
        type: DataTypes.STRING,
        allowNull: false
    }
}, {
    tableName: 'chats',
    timestamps: true,
});


Chat.associate = (models) => {
    Chat.belongsToMany(models.User, { through: models.User_Chat, foreignKey: 'chat_id', otherKey: 'user_id' }); //without otherKey, the table had chat_id and UserId, strangely
    Chat.hasMany(models.Message, { foreignKey: 'chat_id'});
    Chat.belongsTo(models.User, { foreignKey: 'creator_id'});
};

module.exports = { Chat };

User model:

const { sq } = require("../config/db");
const { DataTypes, Sequelize } = require('sequelize');

const User = sq.define("User", {
    id: {
        type: DataTypes.UUID,
        defaultValue: DataTypes.UUIDV4,
        primaryKey: true,
        allowNull: false,
    },
    email: {
        type: DataTypes.STRING,
        allowNull: false,
        validate: {
            is: /^[w-]+(?:.[w-]+)*@(?:[w-]+.)+[a-zA-Z]{2,7}$/
        },
        unique: true
    },
    password: {
        type: DataTypes.STRING,
        allowNull: false,
    },
}, {
    tableName: 'users'
});

User.associate = (models) => {
    User.belongsToMany(models.Chat, { through: models.User_Chat, foreignKey: 'user_id', otherKey: 'chat_id' });
    User.hasMany(models.Message, { foreignKey: 'sender_id' });
    User.hasMany(models.Chat, { foreignKey: 'creator_id' });
};

module.exports = { User }

User_Chat model:

const { sq } = require("../../config/db"); 
const { DataTypes, Sequelize } = require('sequelize');

const User_Chat = sq.define('User_Chat', {
    user_id: {
        type: DataTypes.UUID,
        allowNull: false
    },
    chat_id: {
        type: DataTypes.UUID,
        allowNull: false
    }
}, {
    tableName: 'users_chats'
});

module.exports = { User_Chat }

Initialization of all models:

// Imported models
const UserModel = require('./user').User;
const ChatModel = require('./chat').Chat;
const MessageModel = require('./message').Message;

// Imported junction model(s)
const User_ChatModel = require('./junctions/user_chat').User_Chat;

// Initialize models
const models = {
  User: UserModel,
  Chat: ChatModel,
  Message: MessageModel,
  User_Chat: User_ChatModel
};
console.log('n model index running n');
// Apply associations
Object.keys(models).forEach(modelName => {
    console.log('nmodel name:', modelName, 'associating');
    if (models[modelName].associate) {
    models[modelName].associate(models);
  }
});

module.exports = models;

I have tested querying the junction model directly, which works fine, and I have queried each model directly which also works fine. I added the junction model explicitly (the table was previously being created automatically through associations) after I couldn’t get Sequelize to recognize that I wanted it to use the junction table to match a user to the chats they are a part of. Previously,
it was assuming I wanted to join through the creator_id column. This was my attempt to solve that issue, but it did not work and returned the above error 🙂

My guess is that something is wrong with the way I initialize the models.

EXPECTED:
returning the data from the db with users and chats joined through users_chats where users.id = chats.user_id