How can you implement a v-if directive in a Vue loop based on the maximum numerical value?

Question

How can you implement a v-if directive in a Vue loop based on the maximum numerical value?

I am trying to display an element specifically for the cat with the most kittens, which in this scenario would be Bob:

{
  "cats": [
    {"name": "Tom",
      "kittens": [
        {"name": "Dan"}
      ]
    }
    {
      "name": "Bob",
      "kittens": [
        {"name": "Lil"},
        {"name": "Sue"},
        {"name": "Alf"}
      ]
    }
  }

Ultimately, I want it to look something like this:

<li v-for="cat in cats" :key="cat.name">
  {{ cat.name }}
  <span v-if="cat.kittens.length === biggestNumber">Top parent</span>
</li>

Any tips on how to retrieve, compare and utilize the highest length of the kittens array?

javascript arrays json vue.js vuejs2

Answer 1

Answer №1

To obtain the indexes with the highest lengths of the arrays containing "kittens", you can utilize the computed property:

new Vue({
  el: "#app",
  data() {
    return {
      cats: [
        {"name": "Tom", "kittens": [{"name": "Dan"}]},
        {"name": "Bob", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Kitty", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Ketty", "kittens": [{"name": "Lil"}]}
      ],
    }
  },
  computed: {
    biggestNumber: function() {
      return this.maxIndices(this.cats.map(a => a.kittens.length));
    }
  },
  methods: {
    maxIndices(arr) {
      let maxLength = Math.max(...arr)
      return arr.reduce((m, c, i) => c === maxLength ? m.concat(i) : m,[]);
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<li v-for="(cat, i) in cats" :key="cat.name">
  {{ cat.name }}
  <span v-if="biggestNumber.includes(i)">Top parent</span>
</li>
</div>

Answer 2

To obtain the indexes with the highest lengths of the arrays containing "kittens", you can utilize the computed property:

new Vue({
  el: "#app",
  data() {
    return {
      cats: [
        {"name": "Tom", "kittens": [{"name": "Dan"}]},
        {"name": "Bob", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Kitty", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Ketty", "kittens": [{"name": "Lil"}]}
      ],
    }
  },
  computed: {
    biggestNumber: function() {
      return this.maxIndices(this.cats.map(a => a.kittens.length));
    }
  },
  methods: {
    maxIndices(arr) {
      let maxLength = Math.max(...arr)
      return arr.reduce((m, c, i) => c === maxLength ? m.concat(i) : m,[]);
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<li v-for="(cat, i) in cats" :key="cat.name">
  {{ cat.name }}
  <span v-if="biggestNumber.includes(i)">Top parent</span>
</li>
</div>

Answer 3

Answer №2

Although utilizing a computed property is the preferred approach, I find that @Nikola's response appears to be overly elaborate.

In my opinion, the inclusion of the maxIndices method seems unnecessary in this scenario.

new Vue({
  el: "#app",
  data() {
    return {
      cats: [
        {"name": "Tom", "kittens": [{"name": "Dan"}]},
        {"name": "Bob", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Kitty", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Ketty", "kittens": [{"name": "Lil"}]}
      ],
    }
  },
  computed: {
    mostKittens() {
      return Math.max(...this.cats.map(({ kittens }) => kittens.length));
    }
  }
})

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="a5d3d0c0e5978b938b94">[email protected]</a>"></script>
<div id="app">
  <li v-for="cat in cats" :key="cat.name">
    {{ cat.name }}
    <span v-if="cat.kittens.length === mostKittens">[Top Parent]</span>
  </li>
</div>

Both the above solution and Nikola's answer have a minor flaw. They may both encounter issues if any of your cats lack a `kittens` property.

If you are absolutely certain that such a case will never occur in your component, then the precautions may not be necessary. However, in my view, it's always beneficial to safeguard against potential data inconsistencies. Here’s how I would adjust the code to account for cats without kittens:

new Vue({
  el: "#app",
  data() {
    return {
      cats: [
        {"name": "Tom", "kittens": [{"name": "Dan"}]},
        {"name": "Bob", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Kitty", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Ketty", "kittens": [{"name": "Lil"}]},
        {"name": "Stray Cat"}
      ],
    }
  },
  computed: {
    mostKittens() {
      return Math.max(
        ...this.cats.map(({ kittens }) => kittens?.length || 0)
      );
    }
  },
  methods: {
    isTopParent(cat) {
      return cat.kittens?.length === this.mostKittens;
    }
  }
})

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dfa9aaba9fedf1e9f1eb">[email protected]</a>"></script>
<div id="app">
  <li v-for="cat in cats" :key="cat.name">
    {{ cat.name }}
    <span v-if="isTopParent(cat)">[Top Parent]</span>
  </li>
</div>

Answer 4

Although utilizing a computed property is the preferred approach, I find that @Nikola's response appears to be overly elaborate.

In my opinion, the inclusion of the maxIndices method seems unnecessary in this scenario.

new Vue({
  el: "#app",
  data() {
    return {
      cats: [
        {"name": "Tom", "kittens": [{"name": "Dan"}]},
        {"name": "Bob", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Kitty", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Ketty", "kittens": [{"name": "Lil"}]}
      ],
    }
  },
  computed: {
    mostKittens() {
      return Math.max(...this.cats.map(({ kittens }) => kittens.length));
    }
  }
})

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="a5d3d0c0e5978b938b94">[email protected]</a>"></script>
<div id="app">
  <li v-for="cat in cats" :key="cat.name">
    {{ cat.name }}
    <span v-if="cat.kittens.length === mostKittens">[Top Parent]</span>
  </li>
</div>

Both the above solution and Nikola's answer have a minor flaw. They may both encounter issues if any of your cats lack a `kittens` property.

If you are absolutely certain that such a case will never occur in your component, then the precautions may not be necessary. However, in my view, it's always beneficial to safeguard against potential data inconsistencies. Here’s how I would adjust the code to account for cats without kittens:

new Vue({
  el: "#app",
  data() {
    return {
      cats: [
        {"name": "Tom", "kittens": [{"name": "Dan"}]},
        {"name": "Bob", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Kitty", "kittens": [{"name": "Lil"}, {"name": "Sue"}, {"name": "Alf"}]},
        {"name": "Ketty", "kittens": [{"name": "Lil"}]},
        {"name": "Stray Cat"}
      ],
    }
  },
  computed: {
    mostKittens() {
      return Math.max(
        ...this.cats.map(({ kittens }) => kittens?.length || 0)
      );
    }
  },
  methods: {
    isTopParent(cat) {
      return cat.kittens?.length === this.mostKittens;
    }
  }
})

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dfa9aaba9fedf1e9f1eb">[email protected]</a>"></script>
<div id="app">
  <li v-for="cat in cats" :key="cat.name">
    {{ cat.name }}
    <span v-if="isTopParent(cat)">[Top Parent]</span>
  </li>
</div>

How can you implement a v-if directive in a Vue loop based on the maximum numerical value?

Answer №1

Answer №2

Similar questions

Creating an image gallery with animated effects: A step-by-step guide

Instructions for correctly setting up the test-ai-classifier plugin with appium for selecting UI elements

How can I use Bootstrap to toggle the visibility of one dropdown menu based on the selection made in another dropdown menu?

When performing an Angular HTTP post, additional parameters are automatically included in the request

Attempting to display a collection of 16 diverse images by utilizing the Math.random function in conjunction with a

Finding the total amount in VueJS2

Converting a variable to a string in PHP

Determining the number of words in every line within a textarea

Serialization in Jackson JSON format

Generating elevation graph from a kml file with the combination of php and javascript

Scheduled tasks on Google Cloud Platform's App Engine are failing to run over the weekend

Transmit JSON information to PHP and leverage it for interactions with MySQL database

Is it possible to implement Socket.io in a node.js application without using Express at all?

What is the best way to calculate the average price?

Issue with Angular: Unable to locate a differ that supports the object '[object Object]' of type 'object'. NgFor is only compatible with binding to Iterables such as Arrays

Methods for easily accessing and manipulating arrays

Extracting data from a JSON string within a TXT document

Rails Navigation Issue: JQuery Confirmation Not Functioning Properly

Fetching icon using JavaScript from local file

Load the entire AngularJS webpage using AJAX requests