new Vue({
el:"#exercis",
data:{
effectClasses:{
highlight:false,
shrink:true
}
},
methods:{
}
});
<script src="https://cdn.jsdelivr.net/npm/vue"></script>
<div id="exercise">
<div>
<button @click="startEffect">Start Effect</button>
<div id="effect" :class="effectClasses"></div>
</div>
</div>
#effect{width:100px; height:100px; border:1px solid black;}
.highlight{ background-color:red; width:200px !important; }
.shrink{background-color:gray; width:50px !important;}