css bindng vuejs

https://raw.githubusercontent.com/edwardlorilla/VuejsEssentials/d8082d12b5d3ed4ce7e238cea71ac6f0ffe509fb/index.html

    
    
    
    

        I am a P tag...
    

h1, div, p, span {
            font-size: 66px;
            font-family: helvetica;
        }

        .red_font {
            color: red;
        }

        .blue_background {
            background: blue;
        }

        .heavy_font {
            font-weight: bold;
        }

 new Vue({
        el: "#app",
        data: {
            toggleRedFont: false,
            toggleBlueBackground: false,
            toggleHeavyFont: false
        },
        computed: {
            classObject:function(){
                var vm = this
                return {
                    red_font: vm.toggleRedFont,
                    blue_background: vm.toggleBlueBackground,
                    heavy_font : vm.toggleHeavyFont
                }
            }
        },
        methods: {}
    });