JS Modular Design - context issue

Question

I am just starting to learn the Modular Design principles and I believe I am not understanding the context of one of my methods. In the console, I am getting Uncaught TypeError: Cannot read property 'val' of undefined - line 19. I am using Firebase, if that matters.

Here is my code:

(function(){
    var UpdateTable = {
        resources: Resources,
        init: function(){
            this.cacheDom();
            this.render();
            this.update(snapshot); // Changed this line ///
        },
        render: function(){
            this.resources.on('value', this.update);
        },
        cacheDom: function(){
            this.$table = $('#resourceTable');
        },
        update: function(snapshot){
            console.log(snapshot.val());
            for(var resource in this.resources){
                this.$table.append('<tr><td>' + this.resources[resource].name + '</td><td>' + this.resources[resource].language + '</td></tr>');
            }
        }
    };
    UpdateTable.init();
})();

Answer 1

If you want to make this truly modular, I suggest to pass snapshot as a parameter for your module. This will fix your issue.

(function(snapshot){ // <----- Here I receive snapshot from the invoker
    var UpdateTable = {
        resources: Resources,
        init: function(){
            this.cacheDom();
            this.render();
            this.update(snapshot); // Changed this line ///
        },
        render: function(){
            this.resources.on('value', this.update);
        },
        cacheDom: function(){
            this.$table = $('#resourceTable');
        },
        update: function(snapshot){
            console.log(snapshot.val());
            for(var resource in this.resources){
                this.$table.append('<tr><td>' + this.resources[resource].name + '</td><td>' + this.resources[resource].language + '</td></tr>');
            }
        }
    };
    UpdateTable.init();
})(snapshot); // <---- Here I am passing snapshot from global context to the module context