models.js

NewRect = fabric.util.createClass(fabric.Rect, {
  type: 'newRect',

  initialize: function(options) {
    options || (options = { });

    console.log('initializing NewRect');
    this.callSuper('initialize', options);
  }
});

NewCanvas = fabric.util.createClass(fabric.Canvas, {
  type: 'newCanvas',

  initialize: function(el, options) {
    options || (options = { });

    console.log('initializing NewCanvas');
    this.callSuper('initialize', el, options);
  }
});

view.js

console.log('Starting to load custom objects');
newRect = new NewRect();
console.log(newRect);
newCanvas = new NewCanvas('canvasId');
console.log(newCanvas);