Printing an array of String sent from Spring MVC Controller shows only "toJSON" in javascript

I have a list of String (department names) passed from a controller to a JSP page. I need to get each individual name and use it as the key to a map (the map value will be a list of employees for that department). However, when I do alert for each department name, I got a string "toJSON". How do I get each name in a readable string? Some department name contain special character like apostrophes, slash. Many Thanks!

Controller:

@RequestMapping(value = "/getDepartment", method = { RequestMethod.POST, RequestMethod.GET })
 public ModelAndView getDepartment()
 {
     ModelAndView mv = new ModelAndView();
     mv.addObject("depNameList", depNameList); // depNameList is a type of List<String> 
     mv.setViewName("displayDepartment");
     return mv;
  }

JSP:

 $(document).ready(function() 
 {
    var depArr = "${depNameList}";    
    alert(depArr); // this printed a list of department names
    for ( var i in depArr)
    { 
         alert("i=" + i); // this printed "i=toJSON"
         alert("i=" + JSON.stringfy(i)); // this didn't get invoked.
    }
  });