Is it possible to add multiple javascript objects with the same key to an associative array?

Question

I am working on a Javascript web application (SPA) with RESTful api on the back-end. In my client-side datacontext I want to add objects to my model graph and then send the whole graph to server at once.

Suppose the following example:

I have a Person object in my model which itself has an array of say PhoneNumbers as a property. Now I load a Person from api for edditing and map it to my model. Suppose I want to add some phone number objects to my PhoneNumbers . For this I add each number eg {"id": 0, "number": 6536652226} with an id of zero to my client model and send the whole graph to server when user clicks save. In server I add the objects with the id of zero (new objects) to database with auto-incremented ids.

I am doing my project based on a tutorial. They do something like this to add objects to context:

                var items = {},
                    // returns the model item produced by merging json obj into context
                    mapJsonToContext = function (json) {
                        var id = mapper.getJsonId(json);
                        var existingItem = items[id];
                        items[id] = mapper.fromDto(json, existingItem); //returns the mapped obj
                        return items[id];
                    },
                    add = function (newObj) {
                    items[newObj.id()] = newObj;
                    }

The problem is that if I use this method I wouldn't be able to remove by id the newly-added-not-yet-saved items in client-side 'cause all the ids are zero!

Any suggestions to fix this, or do I need a totally different approach?

Answer 1

First of all, two little misconceptions I've spot:

1) Forget about "associative arrays". Numeric arrays are the only kind arrays you have; the other constructs are just "objects" (this is not PHP).

2) If it's JSON it's a string , not an object.

Other than that, you can of course use an arbitrary value to represent "new" (though I'd probably use null rather than 0 ) as soon as you don't use such value to uniquely identify the yet-to-add item. Eg, this is just fine:

[
    {"id": 0, "number": "6536652226"},
    {"id": 0, "number": "9876543210"},
    {"id": 0, "number": "0123456789"}
]

This is not:

// WRONG!!!!
{
    0: "6536652226",
    0: "9876543210",
    0: "0123456789"
}

}

And of course you cannot find numbers by ID if they still don't have an ID. You need to choose:

• Retrieve the generated ID from DB and update your local data
• Delete by number

Answer 2

Create a localId property on newly created client-side objects, and use that as your key when reconciling server returned-data. Obviously the server would have to return this localId to you.