Building Table Sorting and Pagination in Vue.js

Building Table Sorting and Pagination in Vue.js

Earlier this week I was talking to a good friend of mine (who is also a recent convert to the School of Vue) and he was talking about the troubles he went through in adding table sorting and pagination to a table. He was making use of a particular Vue component that was - to be nice - “undocumented”. While I was reasonable certain that other solutions existed, I thought it would be fun to take a stab at writing my own support for table sorting and pagination. Not a generic solution, but just a solution for a particular set of data.

I began with a Vue app that loaded in data via an Ajax call and rendered a table. This initial version has no sorting or pagination, it just loads data and dumps it in the view. Here’s the layout:

<div id="app">
  
  <table>
    <thead>
      <tr>
        <th>Name</th>
        <th>Age</th>
        <th>Breed</th>
        <th>Gender</th>
      </tr>
    </thead>
    <tbody>
      <tr v-for="cat in cats">
        <td>{{cat.name}}</td>
        <td>{{cat.age}}</td>
        <td>{{cat.breed}}</td>
        <td>{{cat.gender}}</td>
      </tr>
    </tbody>
  </table>
  
</div>

I’ve got a table with four columns: Name, Age, Breed, and Gender. And then I simply loop over my cats to render each row. The JavaScript is simple:

const app = new Vue({
  el:'#app',
  data:{
    cats:[]
  },
  created:function() {
    fetch('https://api.myjson.com/bins/s9lux')
    .then(res => res.json())
    .then(res => {
      this.cats = res;
    })
  }
})

(As an aside, I say it’s simple, but as always, if anything here doesn’t make sense, just ask me in the comments below!) While it isn’t too exciting, you can see this running below.

See the Pen Vue - Sortable Table by Raymond Camden (@cfjedimaster) on CodePen.

Alright, so for the first update, I decided to add sorting. I made two changes to the view. First, I added click handlers to my headers so I could do sorting. Secondly, I switched my loop to use sortedCats, which I’m going to set up as a Vue computed property. Here’s the new HTML:

<div id="app">
  
  <table>
    <thead>
      <tr>
        <th @click="sort('name')">Name</th>
        <th @click="sort('age')">Age</th>
        <th @click="sort('breed')">Breed</th>
        <th @click="sort('gender')">Gender</th>
      </tr>
    </thead>
    <tbody>
      <tr v-for="cat in sortedCats">
        <td>{{cat.name}}</td>
        <td>{{cat.age}}</td>
        <td>{{cat.breed}}</td>
        <td>{{cat.gender}}</td>
      </tr>
    </tbody>
  </table>
  
  debug: sort={{currentSort}}, dir={{currentSortDir}}
</div>

On the JavaScript side, I had to do a few things. First, I added properties to keep track of what I was sorting by and in what direction:

data:{
  cats:[],
  currentSort:'name',
  currentSortDir:'asc'
}

Next, I added the sort method. It has to recognize when we are sorting by the same column and flip the direction:

methods:{
  sort:function(s) {
    //if s == current sort, reverse
    if(s === this.currentSort) {
      this.currentSortDir = this.currentSortDir==='asc'?'desc':'asc';
    }
    this.currentSort = s;
  }
}

Finally, I added my computed property, sortedCats:

computed:{
  sortedCats:function() {
    return this.cats.sort((a,b) => {
      let modifier = 1;
      if(this.currentSortDir === 'desc') modifier = -1;
      if(a[this.currentSort] < b[this.currentSort]) return -1 * modifier;
      if(a[this.currentSort] > b[this.currentSort]) return 1 * modifier;
      return 0;
    });
  }
}

I’m just using the sort method of my array with the property being dynamic. The modifier bit just handles reversing the numbers based on the direction of the sort. You can test this version below:

See the Pen Vue - Sortable Table (2) by Raymond Camden (@cfjedimaster) on CodePen.

By the way, you’ll notice some debug data at the bottom of the view. In a real application I’d remove that, but I used that as a handy way to track values while I was clicking. I could have used Vue DevTools for that, although I’m not certain how well they work with CodePens.

Woot! Almost there! For the final version I added pagination. I didn’t want to add more cats to my JSON data set, so I used a relatively small “page size” of 3. I began by adding buttons to the front end for pagination:

<p>
<button @click="prevPage">Previous</button> 
<button @click="nextPage">Next</button>
</p>

In the JavaScript I made the following changes. First, I added values to track the page size and current page:

data:{
  cats:[],
  currentSort:'name',
  currentSortDir:'asc',
  pageSize:3,
  currentPage:1
},

Next, I added the prevPage and nextPage methods, which were pretty simple:

nextPage:function() {
  if((this.currentPage*this.pageSize) < this.cats.length) this.currentPage++;
},
prevPage:function() {
  if(this.currentPage > 1) this.currentPage--;
}

Finally, I modified my computed property to check the page size and current page values when returning data. I did this via a filter call:

sortedCats:function() {
	return this.cats.sort((a,b) => {
		let modifier = 1;
		if(this.currentSortDir === 'desc') modifier = -1;
		if(a[this.currentSort] < b[this.currentSort]) return -1 * modifier;
		if(a[this.currentSort] > b[this.currentSort]) return 1 * modifier;
		return 0;
	}).filter((row, index) => {
		let start = (this.currentPage-1)*this.pageSize;
		let end = this.currentPage*this.pageSize;
		if(index >= start && index < end) return true;
	});
}

Note the creation of a start and end value. I almost always screw this up so I created variables instead of a super complex if statement. While my code seems to work I’m still not 100% sure that math is right. And here is that final version:

See the Pen Vue - Sortable Table (3) by Raymond Camden (@cfjedimaster) on CodePen.

So that’s it. There is definitely room for improvement. I’d like to add disabled to the buttons when they are at the ‘edge’ and I’d like to highlight, somehow, the table headers when sorting, but I’ll leave that as an exercise to my readers. ;) (Don’t forget you can fork my CodePens and add your own edits!)

Header Photo by Hannes Egler on Unsplash

Raymond Camden's Picture

About Raymond Camden

Raymond is a developer advocate looking for his next gig. He focuses on JavaScript, serverless and enterprise cat demos. If you like this article, please consider visiting my Amazon Wishlist or donating via PayPal to show your support.

Lafayette, LA https://www.raymondcamden.com

Comments