Regex to allow only Positive Number Client Script ServiceNow

function onChange(control, oldValue, newValue, isLoading) {
    if (isLoading || newValue == '') {
          return;
    }
  g_form.hideErrorBox('num');
       var pattern =/^\d+$/;   // regex pattern
   if(!pattern.test(newValue)){
     g_form.showErrorBox('num', getMessage('Please enter Positive number only'));//show error messege
           g_form.setValue('num', '');
   }
}