javascript - Vuejs and Vue.set(), update array

Question

I'm new to Vuejs. Made something, but I don't know it's the simple / right way.

what I want

I want some dates in an array and update them on a event. First I tried Vue.set, but it dind't work out. Now after changing my array item:

this.items[index] = val;
this.items.push();

I push() nothing to the array and it will update.. But sometimes the last item will be hidden, somehow... I think this solution is a bit hacky, how can I make it stable?

Simple code is here:

new Vue({
  el: '#app',
  data: {
  f: 'DD-MM-YYYY',
    items: [
      "10-03-2017",
      "12-03-2017"
    ]
  },
  methods: {
    
    cha: function(index, item, what, count) {
    console.log(item + " index > " + index);
      val = moment(this.items[index], this.f).add(count, what).format(this.f);
  this.items[index] = val;
      this.items.push();
      console.log("arr length:  " + this.items.length);
    }
  }
})

ul {
  list-style-type: none;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/1.0.11/vue.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.10.6/moment.min.js"></script>
<div id="app">
  <ul>
    <li v-for="(index, item) in items">
    <br><br>
      <button v-on:click="cha(index, item, 'day', -1)">
      - day</button>
      {{ item }}
      <button v-on:click="cha(index, item, 'day', 1)">
      + day</button>
    <br><br>
    </li>
  </ul>
</div>

Answer 1

EDIT 2

• For all object changes that need reactivity use Vue.set(object, prop, value)
• For array mutations, you can look at the currently supported list here

---

EDIT 1

For vuex you will want to do Vue.set(state.object, key, value)

---

Original

So just for others who come to this question. It appears at some point in Vue 2.* they removed this.items.$set(index, val) in favor of this.$set(this.items, index, val).

Splice is still available and here is a link to array mutation methods available in vue link.