Having trouble with undefined !== undefined

Question

I'm trying to process a complete function in an ajax call. If the value is undefined, I want cast a var as an empty string. Otherwise, I would like to capture the value into a string array.

The problem is I'm entering the if statement, even when logging the value of the variable in question returns as undefined. What am I missing here?

completefunc: function (xData, Status) {
      $(xData.responseXML).SPFilterNode("z:row").each(function() {
        if(typeof $(this).attr("ows_Products") !== undefined) {
          console.log($(this).attr("ows_Products"));
          arr = $(this).attr("ows_Products").split(',');
        }
        else {
          arr = "";
        }
      });
    }

Answer 1

typeof returns a string value, so you'll need to compare with "undefined" as a string. E.g.,

if(typeof $(this).attr("ows_Products") !== "undefined") { ... }

---

Edit - more info:

If you check out the MDN page for typeof, you'll see this:

The typeof operator returns a string indicating the type of the unevaluated operand.

This is very different from returning the Type itself (which in JavaScript would probably be something like returning a constructor function like String, Array, etc.). Therefore, when using typeof, you'll always be comparing to strings like "object", "string", "undefined", etc.