<script type="text/x-template" id="multi-select-template">
…
   <tr v-for = "(item,index) in columns" 
     @click.exact="AddToOrDeleteFromSelectedColumns"
     @click.shift.exact="AddMultipleToSelectedColumns"
     @click.ctrl.exact="AddToOrDeleteFromSelectedColumns"
     :title="function(item){if(item.longname){return 'Short Name: ' + item.name + '\n----------------\n' + item.longname}else{return item.name}}(item)"
     class="column-list-entry">
   ...
   </tr>
</script>
<script>
Vue.component("multi-select", {
  template: "#multi-select-template",
…
</script>

<multi-select :legend_name="legend_name"
       :columns="columns"
       :selected_columns="selected_columns"
       @update_selected_columns="onSelectedColumnsChange">
</multi-select>

data: function(){
   return {
     legend_name: "Input Columns",
     columns: 
     [
       {"name":"A","longname":"Copper"},
       {"name":"B","longname":"Aluminum Aluminum"},
       {"name":"C","longname":"Calcium"},
       {"name":"D","longname":"Calcium"},
   ],
     selected_columns: [],
   }
 },
... 
methods:{ 
   onSelectedColumnsChange:function(new_columns) {
     this.selected_columns = new_columns;
   },
 },
...