What am I missing for my AngularJS Not Working code? Currently, I'm trying to refactor the AngularJS Working code. From my understanding, the this keyword is equivalent to $scope. Also, for my AngularJS Not Working code I'm trying to understand why it is not working. I've seen working code use this pattern. I'm trying to get more context.
AngularJS Working
<script>
    var app = angular.module("app", []);
    app.controller("ClassController", function ($scope) {
        $scope.classBold = '';
        $scope.classUnderline = '';
        $scope.MakeBold = function () {
            if ($scope.classBold.length == 0) {
                $scope.classBold = 'bold';
            } else {
                $scope.classBold = '';
            }
        };
        $scope.MakeUnderline = function () {
            if ($scope.classUnderline.length == 0) {
                $scope.classUnderline = 'underline';
            } else {
                $scope.classUnderline = '';
            }
        };
    });
</script>
AngularJS Not Working
<script>
(function(){
angular
.module('classApp')
.controller("ClassController", ClassController);
function ClassController($scope){
        var model = this;
        model.classBold = '';
        model.classUnderline = '';
        model.MakeBold = function () {
            if (model.classBold.length == 0) {
                model.classBold = 'bold';
            } else {
                model.classBold = '';
            }
        };
        model.MakeUnderline = function () {
            if (model.classUnderline.length == 0) {
                model.classUnderline = 'underline';
            } else {
                model.classUnderline = '';
            }
        };
    }
    })();
</script>
HTML
    <!DOCTYPE html>
<html>
    <head>
        <title>Demo</title>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.1/angular.min.js"></script>
    </head>
<body>
<div ng-app="classApp" ng-controller="ClassController">
    <p ng-class="SpaceDelimitedClass">Write the class name to apply</p>
    <input type="text" ng-model="SpaceDelimitedClass" placeholder="bold italic overline" />
    <hr />
    <p ng-class="{bold : makeBold, italic : makeItalic, overline : makeOverline}">Apply below style</p>
    <label><input type="checkbox" ng-model="makeBold" />Bold</label>
    <label><input type="checkbox" ng-model="makeItalic" />Italic</label>
    <label><input type="checkbox" ng-model="makeOverline" />Overline</label>
    <hr />
    <p ng-class="[classBold, classUnderline]">Apply Below Class</p>
    <button ng-click="MakeBold()">Make Bold</button>
    <button ng-click="MakeUnderline()">Make Underline</button>
    <hr />
    <p ng-class="[MyStyle, {overline : setIt}]">Write or Apply CSS Class</p>
    <input type="text" ng-model="MyStyle" placeholder="bold or italic or oblic" />
    <label><input type="checkbox" ng-model="setIt" />Overline</label>
</div>
</body>
</html>
CSS
<style>
    .bold {
        font-weight:bold;
    }
    .italic {
        font-style:italic;
    }
    .oblic{
        font-style:oblique;
    }
    .underline{
       text-decoration:underline;
    }
    .overline{
        text-decoration:overline;
    }
</style>
 
    