Question

In comments is output. This is javascript bug, backbone or other?

var t = Backbone.View.extend({
    ben: {},
    banana: function(s){
        this.ben[s] = s;
    },
    show: function(){
        console.info(this.ben)
    }
});
var c1 = new t();
var c2 = new t();
c1.banana('1');
c1.show(); //Object { 1="1"}
c2.banana('2');
c1.show(); //Object { 1="1", 2="2"}

Answer 1

The code is behaving as expected (i.e. not a bug). ben is added to the prototype.

Consider doing this instead:

var t = Backbone.View.extend({
    initialize: function (options) {
        this.ben = {};
    }
    banana: function(s){
        this.ben[s] = s;
    },
    show: function(){
        console.info(this.ben)
    }
});