How to simulate onblur event for a Panel in Extjs

Here is a simple trick in Extjs I borrowed from Ext.layout.BorderLayout that simulates listening for the onblur event of an Ext.Panel. This trick is necessary because unfortunately Ext.Panel does not natively support registering for the onblur event (or at least I don't know how). We typically use this trick when we show a Panel and want to remove it when the user clicks off, or to state it differently, when the Panel looses focus. This is very similar to how menus work.

Step 1: Register for mousedown event

this.panel.show();
Ext.getDoc().on("mousedown", this.handleDocMouseDown, this);

First, we show the panel. Here it is assumed this was created previously. Second, we use Ext.getDoc() to return the current HTML document object, and then we register for the mousedown event. The second parameter, this.handleDocMouseDown, is our function we want called when this event is fired. Notice that we register for the mousedown event as opposed to the click event. This is intentional because listening for the click event will actually call this.handleDocMouseDown before your ready because a click involves both mousedown and mouseup.

Step 2: Handle the event

handleDocMouseDown : function(e) {
if (!e.within(this.panel.getEl())) {
   this.panel.destroy();
   Ext.getDoc().un("mousedown", this.handleDocMouseDown, this);
}
}

In our second step we first check to make sure the user didn't click anywhere in the Panel that was just displayed. If it wasn't then we destroy the panel and unregister the mousedown event.