Vuejs - How to get all unique values in a array (remove duplicates) using v-for

Question

How to show only one button per every distinct date ?

can i use two v-for loops ? how to select distinct values in my loop?

<div v-for="question in allQuestions" >
  <button v-for="date in question.date">
    {{date}}
  </button>
</div>

Data model :

allQuestions : []
question : {'id' : '123' , 'date' : '25'}

Answer 1

You can use Set:

The Set object lets you store unique values of any type, whether primitive values or object references.

MDN's example:

const numbers = [2, 3, 4, 4, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 5, 32, 3, 4, 5]

console.log([...new Set(numbers)])

Just modify it to your needs.

Answer 2

Use reduce to execute a reducer function on each item of the array, then merge the individual matches into the existing object with assign. This merging process takes care of removing (or actually replacing) duplicate items.

const vm = new Vue({
  el: '#app',

  data() {
    return {
      allQuestions: [
        { id: '123', date: '14' },
        { id: '456', date: '2' },
        { id: '933', date: '2' },
        { id: '789', date: '7' },
        { id: '220', date: '14' }
      ]}
  },

  computed: {
    uniqueQuestions() {
      return this.allQuestions.reduce((seed, current) => {
        return Object.assign(seed, {
          [current.date]: current
        });
      }, {});
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>

<div id="app">
  <div v-for="question in uniqueQuestions" :key="question.date">
    <button v-for="date in question.date">
    {{date}}
  </button>
  </div>
</div>