Validation Textbox for Positive Real Numbers using Javascript on Submit button

1.Textbox pid = new Textbox();
2. Button lbl_Submitt = new Button();

lbl_Submit.Attributes.Add("onclick", function checkfornumber() {var msg=''; if(isNan(document.GetElementById("pid.ClientID").value=='')) {msg ='Please Eneter Positive Real Numbers'; alert(msg); return fase;}}return checkfornumber(););


isNan() ; // Checks weather input is number or not