When looping through this string, the alert prints out test 4 times (correctly) but then also prints "undefined" at the end. How do I make it doesn't return undefined.

This returns - undefinedCAFE ::

```
alert(match("abcdef", "CAfe"));

function match(string, pattern) {

    var patternUpperCase = pattern.toUpperCase();
    var stringUpperCase = string.toUpperCase();
    var stringConcatenate;
    var answer;

    for (var i = 0; i < patternUpperCase.length; i++) {
        if (patternUpperCase.charAt(i) != undefined) {
            if (patternUpperCase.charAt(i) >= 'A' && patternUpperCase.charAt(i) <= 'Z') {
                stringConcatenate += patternUpperCase.charAt(i);
                alert("test");
            }
        }
    }
    return stringConcatenate;
}

```

This is what the function needs to do: returns true if all the individual LETTERS of pattern appear in string (regardless of order) (case insensitive)

Examples
 match("abcdef","@C2D!") returns true
 match("abcdef","CAfe") returns true
 match("abcdef","CG") returns false