Sequelize: Require vs Import

Question

In the documentation for sequlize they use the import function like so

// in your server file - e.g. app.js
var Project = sequelize.import(__dirname + "/path/to/models/project")

// The model definition is done in /path/to/models/project.js
// As you might notice, the DataTypes are the very same as explained above
module.exports = function(sequelize, DataTypes) {
  return sequelize.define("Project", {
    name: DataTypes.STRING,
    description: DataTypes.TEXT
  })
}

However, what would be so wrong with this?

// in your server file - e.g. app.js
var Project = require(__dirname + "/path/to/models/project")

// The model definition is done in /path/to/models/project.js
  var Project = sequelize.define("Project", {
    name: Sequelize.STRING,
    description: Sequelize.TEXT
  });
module.exports = Project

Answer 1

Well, as you can see your model definition needs two things:

1. Sequelize or DataTypes
2. sequelize

In your first example when using sequelize.import('something'); it is similar to use require('something')(this, Sequelize); (this being the sequelize instance)

Both are necessary to initialize your model, but the important thing to understand is: One of these is a classtype so it's global, the other one is an instance and has to be created with your connection parameters.

So if you do this:

 var Project = sequelize.define("Project", {
    name: Sequelize.STRING,
    description: Sequelize.TEXT
  });
module.exports = Project

Where does sequelize come from? It has to be instantiated and passed somehow.

Here is an example with require instead of import:

// /path/to/app.js
var Sequelize = require('sequelize');
var sequelize = new Sequelize(/* ... */);
var Project = require('/path/to/models/project')(sequelize, Sequelize);

// /path/to/models/project.js
module.exports = function (sequelize, DataTypes) {
    sequelize.define("Project", {
       name: DataTypes.STRING,
       description: DataTypes.TEXT
    });
};

module.exports = Project

You could even change it so you wouldn't have to pass Sequelize by requiring it in the model itself, but you would still need to create a sequelize instance prior to define the model.