Question

var O = {

    elements: {

        main: function() { return jQuery("#main"); },
        footer: function() { return jQuery("#footer"); }
    },

    main: function(html) {

        return (this.elements.main());
    },


    style: {

        setMaincolor: function() {

            // TypeError: Cannot call method 'main' of undefined
            return (this.elements.main());

        }

    }    

};

so; I’m O.style Object parents Objects ????

O.style.setMaincolor() // TypeError: Cannot call method 'main' of undefined
O.main() // [<div id=​"main">​</div>​]

setMaincolor method return this to O Object

Answer 1

this refers to the object on which the method was invoked.

main() is invoked on the O object, so this is a reference to O. Therefore this.elements === O.elements.

setMaincolor() is invoked on the style object, so this will be a reference to O.style, which does not have an .elements property.