SCRIPT438: Object doesn't support property or method 'match'

SCRIPT438: Object doesn't support property or method 'match'

I keep getting the error " SCRIPT438: Object doesn't support property or method 'match' "

Its a simple text box the user enters numbers only into. Here's the code for my function: 
  
    
   
  1. function IsNumeric(item, message, scrollTo, focus) {
    2. 
   
  2.     var numExp = /[0-9 -()+]+$/;
    3. 
   
  3.     var aReturn;
    4. 
   
  4.     aReturn = $('#' + item).match(numExp);
    5. 
   
  5.     if (message && !aReturn) alert(message);
    6. 
   
  6.     if (scrollTo && !aReturn) ScrollToPosition(0, scrollTo);
    7. 
   
  7.     if (focus && !aReturn) { $('#' + item).focus(); ScrollToElement(item); }
    8. 
   
  8.     return aReturn;
    9. 
   
  9. }
    10. 
   
  10.     aReturn = IsNumeric('RentalPropertyZip', 'Please enter a valid zip code.', null, true);
    11. 
   
  11.     if (!aReturn) return aReturn;
    12.