om/public/routes/msgCard.js

Vue.component('MsgCard', {
    template: `<div class="om-card card">
                <h6 class="msg-head">
                <b>{{ msg.subject }}</b>
                <img src="favicon.ico" width=20px height=20px>
                </h6>
                {{ msg.message }}<br><br>
                <a v-for="tag in msg.tag" href="#">#{{ tag }} </a>
				</p>
                <div class="om-card-footer"> <div class="om-user-line">
                <i class="material-icons">account_circle</i>
                Erstellt von {{ msg.user }}</div>
                <i class="material-icons" @click="myFilter()" v-if="!isActive">bookmark_border</i>
                <i class="material-icons" @click="myFilter()" v-else="isActive">bookmark</i>
                </div></div>`,
    props: ['msg'],

    data: function () {
        return {
            isActive: false,
        };
    },

    methods: {
           myFilter: function() {
            this.isActive = !this.isActive;
        },
    }
});