gistfile1.js

var Sequelize = require('sequelize'),
	sequelize = new Sequelize('sequelize_test', 'sequelize_test', 'YDLvjZJv9GdvbM8G', {
		syncOnAssociation: false,
		logging: console.log
	});

var User = sequelize.define('User', {}),
	Post = sequelize.define('Post', {}),
	SharedPosts = sequelize.define('SharedPosts', {})

Post.belongsTo(User, {as: 'Creator', foreignKey: 'creator_id', foreignKeyConstraint: true});
User.hasMany(Post, {foreignKey: 'creator_id'});

User.hasMany(Post, {as: 'SharedPosts', joinTableModel: SharedPosts, foreignKey: 'user_id'}); // , foreignKey: 'user_id', foreignKeyConstraint: true
Post.hasMany(User, {as: 'SharedWithUsers', joinTableModel: SharedPosts, foreignKey: 'post_id'}); // , foreignKey: 'post_id', foreignKeyConstraint: true

sequelize.sync({force: true}).done(function (err) {

});