Sequelize.define is not a function

When you encounter the error “sequelize.define is not a function” in your JavaScript code while working with Sequelize, it typically means that you have not correctly imported or initialized the Sequelize module. In order to use the Sequelize library and its functions, you need to ensure that you properly set up the Sequelize instance.

Here is an example of how you can define a Sequelize model:

    
      const { Sequelize, DataTypes } = require('sequelize');
      
      // Create a new instance of Sequelize
      const sequelize = new Sequelize('database', 'username', 'password', {
        host: 'localhost',
        dialect: 'mysql',
      });

      // Define a model
      const User = sequelize.define('User', {
        firstName: {
          type: DataTypes.STRING,
          allowNull: false
        },
        lastName: {
          type: DataTypes.STRING,
          allowNull: false
        },
        age: {
          type: DataTypes.INTEGER,
          allowNull: true
        }
      });

      // Sync the model with the database
      sequelize.sync()
        .then(() => {
          console.log('Model synced with the database');
        })
        .catch((error) => {
          console.error('Error syncing model:', error);
        });
    
  

In this example, we first import the necessary modules from Sequelize. Then, we create a new instance of Sequelize by passing the database credentials and connection details. After that, we define a model called “User” with specified attributes and their data types. Finally, we synchronize the model with the database using the sequelize.sync() function.

Make sure you have installed Sequelize using npm or yarn before trying to use it: npm install sequelize or yarn add sequelize.