Adding items to a javascript array

Question

Hi,

I'm attempting to assign items to an array on a users action, so for example, user clicks "Add", this will add the selected id into the relevant section of the array.

The array won't be created at first so I set up an empty array:

var Options={};

On the users click, I then want to assign a key to match the option selected from a drop down so I can use this as a reference later on.

E.g. When the user clicks plus on a record, the option selected from a drop-down is 2. The id of the record they selected is say 5.

I'd like to structure my array like the following:-

[key e.g drop down option] => 'records' => array [record_id]

Each time the user clicks plus next to a record, the id is appended to the correct array based on the drop down selected option.

[option 1] => 'publication_date' = 12/09/2010, 'records' => [1, 2, 4]
[option 2] => 'publication_date' = 15/09/2010, 'records => [1, 3, 5]

etc, each option from the select box has a publication date and a series of records the user can assign to it.

Answer 1

You can do something like this:

function AddItem(key, value)  {
   if(Options[key]) Options[key].push(value);
   else Options[key] = [value];
}

For example doing this:

​AddItem(2, 5);
AddItem(2, 6);

Would result in Options being:

{ 2: [5, 6] }

You can give it a try/play with it here.

Answer 2

An object in javascript is good to store a one key dataset not various keys.

ie: var records = {'12/09/2010':[1, 2, 4], '15/09/2010':[1, 3, 5]}

To get the records for the 15/09: records['15/09/2010']
Add a new record for a date: records['15/09/2010'].push(6)

If the date change, you need to do something like:
records['17/09/2010'] = records['15/09/2010']; delete records['15/09/2010']

The user is not able to change both at the same time(date and add) and you should do both update actions separately.

---

Now if you plan to have more keys, you should use an array of objects:

var records = [
  {publication_date:'12/09/2010', records:[1, 2, 4], ..., otherProp='...'},
  ...
];

And for each change, loop on the array, find the relevant item and change it.