How can I validate data in Sequelize with Node.js?

How can I validate data in Sequelize with Node.js?

You can use the validate option in your model definitions to enforce validation rules. For example, you can specify that a field must be unique or not null.

Can you give me an example of a model with validation?

Sure! Here's a simple example:

const User = sequelize.define('User', {
  username: {
    type: Sequelize.STRING,
    allowNull: false,
    unique: true,
    validate: {
      len: [3, 20], // username must be between 3 and 20 characters
    }
  },
  email: {
    type: Sequelize.STRING,
    allowNull: false,
    validate: {
      isEmail: true, // must be a valid email format
    }
  }
});

What happens if the validation fails?

If validation fails, Sequelize will throw a SequelizeValidationError, and you can catch this error to handle it appropriately in your application.