title: How to set a default value for <v-select> that will update value if user changes the selection in Vue.js
body: <p>I have searched online and have not found an answer to this Vue.js question. 
  I am pretty new to Vue.js. In my form, there is a  drop down for end time which gives a choice of times to choose from. The default for this field is 30 minutes after start time, but the user can change this value. For now, the user is able to change the displayed time for end time, but the data property <strong>end_time is not getting changed</strong>. I need this value to update (not just stay at the default) so I can use it to calculate duration from start time to end time. Code is below. Thanks for the help in advance.</p>
  
  <p>v-select:</p>
  
  <pre><code> &lt;v-select
        :items="times"
        :value="getEndTime"
        label="End Time"
        box
        placeholder="End Time"
  
      &gt;&lt;/v-select&gt;
  </code></pre>
  
  <p>part of my data object (note: end_time)</p>
  
  <pre><code>export default {
  data: () =&gt; ({
  
    date: new Date().toISOString().slice(0,10),
    menu2: false,
    times: [],
    start_time: '',
    end_time: '',
  </code></pre>
  
  <p>from <code>methods:</code> section:</p>
  
  <pre><code>getStartTimeIndex()
    {
  
            // looking for index of start_time in times array
            var startTimeIndex=0;
  
            for(var x =0; x&lt;this.times.length;x++)
            {
              if(this.times[x] == this.start_time)
              {
                startTimeIndex = x;
                break;
              }
  
            }
  
            return startTimeIndex;
    }
  </code></pre>
  
  <p>from <code>computed:</code> section:</p>
  
  <pre><code>getEndTime()
    {
  
  
         var startTimeIndex = this.getStartTimeIndex();
  
              //if start time is set and end time is not:
          if (this.start_time != '' &amp;&amp; this.end_time == '')
          {
  
             this.end_time = this.times[startTimeIndex + 2]; // two 15 min. increments is 1/2 hr. later
             console.log("getEndTime(): startTimeIndex = " + startTimeIndex);
  
         }
  
              return this.end_time;
  
  
    }
  </code></pre>