So… the graphing library look damn good, but focusing more on the nutts & bolts.

Previously ExtJS has had an on demand instantiation system vi anoymous objects with a property of xtype. It’s fairly likely that not every component of an ExtJS enhanced page is going to be used by a user or even looked at, so the xtype support allowed for avoiding costly and wasted object/component instantiations.

Now it looks like they’re taking that one step further. Looking at the Public Release 3 of ExtJS 4’s documentation, I noticed some new additions… specifically lazy class loading. If I’m correct in my assumptions, that means that instead of loading the ENTIRE ExtJS library and possibly only using a tiny bit of it, you can load up only what you need saving rendering time & bandwidth!

Ext.require([
    'widget.window',
    'widget.button',
    'layout.fit'
]);

Ext.onReady(function() {
    var window = Ext.widget('window', {
        width: 500,
        height: 300,
        layout: 'fit',
        items: {
            xtype: 'button',
            text: 'Hello World',
            handler: function() { alert(this.text) }
        }
    });

    window.show();
});

Authoritative source here