How to restrict text box to enter only numerics with + - and .

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Javascript

Iam writing a function on onkeydown and onpress event
like below

function isNumberKey(evt)
      {
         var charCode = (evt.which) ? evt.which : event.keyCode
         if (charCode != 46 && charCode > 31 && (charCode < 48 || charCode > 57&& charCode != 190 && charCode != 110 && (charCode > 105 || charCode < 96||))
            return false;

         return true;
      }

It is accessing + and - of the number pad but when am trying to enter + and - from keybord padds
i.e by using shift + = for plus and shift +- for minus
it is not allowing to enter + and - because the event is firing on pressing of shift only how to make text box to allow numbers qith plus and minus symbol using key board