sequelize.js - Sequelize Subtype Example -

i trying replicate example here simple crud operations. have difficulty accessing shared foreign key in example , setting it. suggestions on how can access 'commentable' field of comment object? due {constraint: false} (foreign key constraints not being generated) it's not being making sense.

here working example:

var sequelize = require('sequelize'); var sequelize = new sequelize(   'my_test', // db name   'postgres', // username   'postgres', // password   {     host: 'localhost',     dialect: 'postgres',     port:5432,     dialectoptions: {         ssl: false     },     logging: true, //verbose     pool: {       max: 5,       min: 0,       idle: 10000     }   } );   // define models  var image = sequelize.define('image', {   title: sequelize.string });  var post = sequelize.define('post', {   title: sequelize.string });  var comment = sequelize.define('comment', {   title: sequelize.string,   commentable: sequelize.string,   commentable_id: sequelize.integer } , {   instancemethods: {     getitem: function() {       console.log(this);       console.log('====================');       console.log('====================');       //console.log(this.gettitle());        //console.log(this.getcommentable());       console.log('====================');        return this['get' + this.commentable.substr(0, 1).touppercase() + this.commentable.substr(1)]();        //where definition of method? getimage/getpost.     }   } } );   // relations // post-comment post.hasmany(comment, {  //adds fk in comment   foreignkey: 'commentable_id',   constraints: false,   scope: {     commentable: 'post'   } });  comment.belongsto(post, {   // fk on src (comment)   foreignkey: 'commentable_id',   constraints: false,    as: 'post' });  // image-comment image.hasmany(comment, {      //adds fk in comment   foreignkey: 'commentable_id',   //as:'commentableid',   constraints: false,   scope: {     commentable: 'image'   } }); comment.belongsto(image, {    // fk on src (comment)   foreignkey: 'commentable_id',   constraints: false,   as: 'image' });  //=========  sequelize.sync()   .then(function () {     console.log('---------- sync');     var image1 = image.build({title: 'very_important_task.jpg'});     var image1promise = image1.save()                               .then(function(i){                                  var commentpromise=i.createcomment({ //create comment through image sets commentable , commentable_id                                   title: 'my comment 999999999'                                 });                                  // break previous promise abel access image1 when keep on adding chain                                 commentpromise                                   .then(function(c){  // comment saved.                                     console.log('##################### comments: ');                                     image1.getcomments()                                           .then(function(results){    //results[0] first result                                             console.log(                                                results.map(                                                 function(item) {                                                   return item['title']; //or image.title         item.commentable_id  === image id                                                 }                                               )                                             );                                           });                                       // after comment creation check accessing comentable reference of comment                                     c.getitem()                                      .then(function(i){                                         console.log(i.title)                                       });                                 });         //creat lots of comments        comment.bulkcreate([          {title: 'my comment 1', commentable_id:image1.id, commentable:'image'},          {title: 'my comment 2', commentable_id:image1.id, commentable:'image'}       ]).then(function() {           image1.getcomments()                 .then(function(results){                   console.log(                     results.map(                       function(item) {                         return item['title'];                       }                     )                   );                 });          });      }); //save promise of image make sure created code accessing   });