I got the answer for this question.
this line :
createNumberLine.AddEventListener("click", CreateNumberLine, false);
should be replaced by :
if (Script.isNotNullofUnDefined)
{
createNumberLine.AddEventListener("click", CreateNumberLine, false);
}
or
createNumberLine.AddEventListener("click", delegate(ElementEvent e)
{
CreateNumberLine;
}, false);