Only allow numbers, decimals, negative

Question

I have this code that only permits numbers to be entered in an input field on keypress()

if (e.which != 8 && e.which != 0 && (e.which < 48 ||          


        

Answer 1

Here is a working demo that checks whether the number is valid or not and also doesn't allow multiple signs:

$("#num").on('keyup', function() {
  if ($.isNumeric($(this).val())) {
    console.log('Valid!');
  } else {
    console.log('Invalid!');
  }
});