Model.Foo = function() {
    // private stuff
    var a, b;

    // method which accesses the variable `a`
    this.func = function() {
        window.alert(a);
    };

    // public properties
    this.attr1 = '';
    this.attr2 = '';
};

Model.Foo.prototype = {
    func1 : function() { /* ... */},
    func2 : function() { /* ... */}
    //,other prototype functions
};