How can I implement data validation in Sequelize?

How can I implement data validation in Sequelize?

You can implement data validation in Sequelize by using the validate property in your model definitions. For example, you can specify that a field must be an integer or a string with a certain length.

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,
    validate: {
      len: [3, 20], // username must be between 3 and 20 characters
    }
  },
  age: {
    type: Sequelize.INTEGER,
    validate: {
      isInt: true, // age must be an integer
      min: 0 // age must be at least 0
    }
  }
});

What happens if the validation fails?

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