Misunderstanding a javascript execution flow

Question

i'm starting with Backbone and i'm writing an application for cellphones sales. But my doubt is about the javascript execution flow specifically.

The situacion is that i have a custom method to deny duplicates on my cart collection, these method is something like this:

var Cart = Backbone.Collection.extend({
            contains : function(aProduct){
                _.each(this.models, function( element, index, list ){
                    if( element.get('product').get('id') == aProduct.get('id') ){ 
                        return true; 
                    }
                });
                return false;
            }
        });

The method detects the duplicates and try to return true, but that line isn't the last one, because the last statement executed was the "return false". At this point i realize that i have a misunderstanding in this javascript execution flow.

maybe one of you can enlight me with your knowledge

thanks

Answer 1

You are returning true from the function you passed into _.each. That is different from your contains function. Here is a way to get it working:

var Cart = Backbone.Collection.extend({
            contains : function(aProduct){
                var doesContain = false;
                _.each(this.models, function( element, index, list ){
                    if( element.get('product').get('id') == aProduct.get('id') ){ 
                        doesContain = true; 
                    }
                });
                return doesContain;
            }
        });

However, an even better way (assuming that is lodash or underscore), would be to use _.any

var Cart = Backbone.Collection.extend({
            contains : function(aProduct){
                return _.any(this.models, function( element ){
                    if( element.get('product').get('id') == aProduct.get('id') ){ 
                        return true; 
                    }
                });
            }
        });