2-tier or N-tier on client side?

[qiuyl]

Usually we choose a 3-tier or N-tier structure for database driven website developement. With AJAX, do we need a 2-tier or N-tier on client side?

For example, I usually use data model (DM) in js for grid, view, content panel. The js code for DM is usually mixed with other UI interface in one class. How can I effectively have a seperate class, for example datamodel class, which is exclusive for data access? In this way the DM code can be reused in many pages.

I am a newbie in ajax application developement. All of the time I need your guys help!

Thank you!

[jack.slocum]

Extending the appropriate data model class always an option. Then you can add additional helper functions as well. For example:


FeedDataModel = function(){
var schema =
... // put your data model init and config stuff here
// you can optionally pass paging init info to this
// objects constructor and call initPaging with it
}
YAHOO.extendX(FeedDataModel, YAHOO.ext.grid.XMLDataModel, {
loadFeed : function(feedUrl){
this.load('feed-proxy.php', {feed: feedUrl});
}
});

then anywhere you need a new data model for feeds:

var dm = new FeedDataModel();
dm.loadFeed('http://www.jackslocum.com/blog/feed');