You can pass string parameters to JavaScript functions like below code:
I passed three parameters where the third one is a string parameter.
var btn ="<input type='button' onclick='RoomIsReadyFunc(" + ID + "," + RefId + ",\"" + YourString + "\");' value='Room is Ready' />";
// Your JavaScript function
function RoomIsReadyFunc(ID, RefId, YourString)
{
alert(ID);
alert(RefId);
alert(YourString);
}