Question

I’m developing a HTML 5 application.

In Javascript I have defined a custom class and a HashTable implementation:

function Card(newId, newName, newDescription)
{
    this.id = newId;
    this.name = newName;
    this.description = newDescription;
}

function HashTable()
{
    var hashTableItems = {};

    this.SetItem = function(key, value)
    {
        hashTableItems[key] = value;
    }

    this.GetItem = function(key)
    {
        return hashTableItems[key];
    }
}

I use HashTable to add Card’s objects. I use this code to add cards:

...
var card = new Card(id, name, description);

$.viacognitaspace.cards.SetItem(id, card);
...

My problem is when I call HashTable.GetItem and I don’t know how to cast object returned to Card class.

var cardObject = $.viacognitaspace.cards.GetItem(cardNumber);

Here, cardObject is undefined.

If I do this:

$('#cardName').text(cardObject.name);

I get an error.

How can I fix this?

Answer 1

Try modifying your code to the following:

$.viacognitaspace = {} /* define namespace if not already defined... */

var card = new Card(id, name, description);

/* the "new" keyword creats an instance of your HashTable function
   which allows you to reference and modify it later on... */
$.viacognitaspace.cards = new HashTable();

$.viacognitaspace.cards.SetItem(id, card);

You also need to create an instance of the HashTable function.

Example:

http://jsfiddle.net/3BWpM/