JavaSscript TextArea Character counter

character-counter.js

App.questionnaire.TextAreaCharacterCounter = function () {
    var textMax = 300,
        textAreas = ['summary', 'directions'];

    textAreas.forEach(function(textArea) {
        var $textArea = $('#' + textArea);
        
        App.questionnaire.updateTexAreaDescriptionWithCharacterCount($textArea, textMax);

        $textArea.on('focus keyup' , function () {
            App.questionnaire.updateTexAreaDescriptionWithCharacterCount($textArea, textMax);
        });
    });
};

App.questionnaire.updateTexAreaDescriptionWithCharacterCount = function(textArea, textMax) {
    var $feedbackArea = $('.FormItem--' + textArea.attr('id') + ' .FormItem-description'),
        textLength = App.questionnaire.getUTF8Length(textArea.val()),
        textRemaining = textMax - textLength;

    if (textRemaining < 0) {
        textRemaining = '<span style="color: red;">' + textRemaining + '</span>';
    }

    $feedbackArea.html(textRemaining + ' characters remaining');
}

App.questionnaire.getUTF8Length = function(string) {
    var utf8length = 0;
    
    for (var n = 0; n < string.length; n++) {
        var c = string.charCodeAt(n);
        if (c < 128) {
            utf8length++;
        }
        else if((c > 127) && (c < 2048)) {
            utf8length = utf8length+2;
        }
        else {
            utf8length = utf8length+3;
        }
    }
    
    return utf8length;
}