UserScript for opera duckduckgo fix onkeypress not detected

duckduckgo.user.js

// ==UserScript==
// @name           
// @namespace      events.script
// @include        http://duckduckgo.com/*
// @include        https://duckduckgo.com/*
// @match          http://duckduckgo.com/*
// @match          https://duckduckgo.com/*
// @run-at document-end
// ==/UserScript==
(function () {
	function forwardEvents(){
		if(!Array.prototype.contains) Array.prototype.contains = function(obj) {
			var i = this.length;
			while (i--) {
				if (this[i] == obj) {
					return true;
				}
			}
			return false;
		}
		var codes=[
			/*ESC:*/ 27,
			/*TAB:*/ 9,
			/*RETURN:*/ 13,
			/*UP:*/ 38,
			/*DOWN:*/ 40,
			/*LEFT:*/ 37,
			/*RIGHT:*/ 39
		];
		document.onkeydown = function(e){
			e = e || window.event;
			var target = e.target || e.srcElement;
			if(!codes.contains(e.keyCode)){
				return true;
			}
			if(document.createEventObject)
			{
				var eventObj = document.createEventObject();
				eventObj.keyCode = e.keyCode;
				target.fireEvent("onkeypress", eventObj);   
			}else if(document.createEvent)
			{
				var eventObj = document.createEvent("Events");
				eventObj.initEvent("keypress", true, true);
				eventObj.which = e.keyCode;
				eventObj.keyCode = e.keyCode;
				target.dispatchEvent(eventObj);
			}
 			return true;
		};
	}
	var isOpera = Object.prototype.toString.call(window.opera) == '[object Opera]';
	if(!isOpera){
		return;
	}
	if(document.body){
		forwardEvents();
	} else {
		window.addEventListener('DOMContentLoaded',function(e){forwardEvents();});
	}
})();