Javascript detect DOM ready

I am going to provide you pure javascript code to check DOM is ready or not. Please see below code,once DOM has been full loaded it will alert "Developer Gang".

window.dg = {

       //check dom is ready or not
	domReady: function(callback) {
	(document.readyState === "interactive" || document.readyState === "complete") ? callback() : this.addEvent(document, "DOMContentLoaded", callback);
	},
	//Event listener for all browsers
	addEvent: function (obj, e, callback) {
	if(obj.addEventListener)
	obj.addEventListener(e, callback, false);
	else if(obj.attachEvent)
	obj.attachEvent("on" + e, callback);
	},
	developerGang:function(){
	  
	  alert('Developer Gang');
	
	},
	init:function(){
	      //When DOM has been fully loaded
		this.domReady(function(){	
		    dg.developerGang();
		});
	}

}

//call init
dg.init();