Select2 Cascade (for v4.x)
=============================

Loadeding/refreshing options of a select2 list box using ajax based on selection of another select2 list box.

How to use
--------------
Create a new instance of `Select2Cascade` by passing the following 4 things -
* Parent select2 listbox
* Child select2 listbox
* URL to load child items on selection changed
* Optional data object to be sent with request. The selected value of parent select2 listbox will be set in this data object as `parent_id` 

The response json should be a flat object of value:label pairs. e,g,
```JavaScript
{
  20150415: "Chittagong Zila",
  20190901: "Comilla Zila",
  20221601: "Cox's Bazar Zila",
  20301401: "Feni Zila"
}
```

Examples
----------
When `#parentList` is changed, call to */path/to/geocode?type=district&parent_id=SELECTED-PARENT*
and set the options of `#childList` from the ajax response.
```JavaScript
new Select2Cascade($('#district'), $('#zila'), 'path/to/geocode', {type:"district", parent_id: ''});
new Select2Cascade($('#zila'), $('#thana'), 'path/to/geocode', {type:"zila", parent_id: ''});
```

If you want to do something with the response data or selectboxes, you can set (any number of) 
callbacks to be executed after the child listbox refreshed -
```JavaScript
var cascadLoading = new Select2Cascade($('#parent'), $('#child'), 'path/to/geocode', {type:"child", parent_id: ''});
cascadLoading.then( function(parent, child, items) {
    // Open the child listbox immediately
    child.select2('open');
    // Dump response data
    console.log(items);
})
```