Validating input characters for numbers using javascript

Javascript code:

 

function isNumeric()

{

if(((window.event.keyCode >= 48) && (window.event.keyCode <= 57)) || ((window.event.keyCode >= 96) && (window.event.keyCode <= 105)) || ((window.event.keyCode == 8) || (window.event.keyCode == 9) || (window.event.keyCode == 46) || (window.event.keyCode == 35) || (window.event.keyCode == 36) || (window.event.keyCode == 37) || (window.event.keyCode == 39)))

      {

            return true;                       

      }

      else

      {

            return false;

      }

}