. For example, to show our message when any paragraph in our test page is clicked, what is the extjs code on paragraph click?

Ext.onReady(function() {
Ext.select('p').on('click', function() {
alert("You clicked a paragraph");
});
});

or

Ext.onReady(function() {
var paragraphClicked = function() {
alert("You clicked a paragraph");
}
Ext.select('p').on('click', paragraphClicked);
});