btnCount.addEventListener(MouseEvent.CLICK, countVowels);
txtinSentence.addEventListener(MouseEvent.CLICK, clearLabels);
function countVowels(e:MouseEvent):void {
    var phrase: String;
    var current_char: String;
    var is_vowel: Boolean;
    var num_vowels: int;
    var vowel_types: String;

    vowel_letters = "aeoui";
    phrase = txtinSentence.text;


    // iterate through each char, looking for vowels
    for (i = 0; i < str.length; i++) {  // 'i' is a counter
        current_char = phrase.charAt(i);    // use 'i' to index the phrase
        if(vowel_letters.indexOf(current_char) >= 0) {   // actionscript is horrible
            num_vowels += 1;    // yay there's a vowel
        }
    }

    // output the text
    lblOutput.text += "There are " + num_vowels + " in the sentence";

}