time_diff.html

<script src="https://cdn.jsdelivr.net/npm/vue"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment-with-locales.js"></script>

<div id="app">
  <input v-model="mytime">
  <p>
  <p>FromNow : {{ time_diff() }}
  <p>Diff(sec) : {{ time_diff_sec() }}
</div>

<script>
var app = new Vue({
  el: '#app',
  data: {
    mytime: moment().format("YYYY/MM/DD HH:mm:ss"),
  },
  methods: {
    time_diff: function(){
      moment.locale('ja')
      return moment(this.mytime).fromNow()
    },
    time_diff_sec: function(){
      return moment(this.mytime).diff(moment(),'seconds')
    } 
  }
})
</script>