正则 过滤敏感字

<script>
		window.onload = function(){
			
		
			var oTxt1 = document.getElementById("txt1");
			var oTxt2 = document.getElementById("txt2");
			var oBtn = document.getElementById("btn");
			
			oBtn.onclick = function(){
				var reg = /北京|淘宝|百度/g;
				
				oTxt2.value = oTxt1.value.replace(reg,'***');
			}
		}	
		</script>

　　

<textarea id="txt1" name="" rows="" cols=""></textarea><br />
		<input id="btn" type="button" value="过滤" /><br />
		<textarea id="txt2" name="" rows="" cols=""></textarea>