Regex to allow only numeric data in a single line field Client Script ServiceNow

function onChange(control, oldValue, newValue, isLoading) {
      if (isLoading || newValue == '') {
      return;
      }
      var regexNumber = /^[+]?\d*$/;
      if(!regexNumber.test(newValue)){
      alert('Please enter numeric value');
      g_form.setValue('num','');
      }
    }