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Implementing Drag and Drop in Vuejs

suniljoshi19 profile image Sunil Joshi Originally published at wrappixel.com ・5 min read

In this article we will be implementing something fun. We will be implementing the drag and drop feature in Vuejs. I know there are a whole lot of libraries out there that will help you set this up but its always a good idea to understand how its working under the hood.

Since its a very small application, we won’t be making use of the Vue CLI, rather we will be using the Vuejs script tag. This also gives us all the ability our CLI would give us.

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We will start by setting up our project directory, We will create a folder in our desktop directory, This is where we will be setting up our application.

Basically we will need just two files, an index.html file and a main.js file. All our template codes will go to the index.html file and all our Vuejs codes will go to the main.js file.

Vue Drag and Drop Image Upload

To do this open up your terminal and type the following:

cd desktop && mkdir vuedragndrop && cd vuedragndrop
touch index.html && touch main.js
code .

This command will create this files inside our directory and open up the directory in VS code.

We will start by modifying our index.html file by adding the custom html 5 boilerplate and then add the Vue script tags:

    <!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
        <script src="https://cdn.jsdelivr.net/npm/vue"></script>
    </head>
    <body>
        <div id="app">
            {{message}}
        </div>
        <script src="main.js"></script>
    </body>
    </html>

We start by defining the HTML 5 boilerplate and the add the Vuejs script tag in the head tag, this will initialise Vuejs immediately when the page is loaded. We then create a div with an id of app, this is where we will be writing all our Vuejs code. You have to run your application on a live-server. You could use NPM to install any live-serve of your choice.

After doing this we need to create the Vuejs instance in our main.js file:

var app = new Vue({
    el: '#app',
    data: {
        message: 'Hello Vue!'
    }
})

We use the new Vue() method to create an instance of Vuejs and the define the message data property that we reference in our index.html file.

We will create a simple user interface that will show the drag and drop point.Add the following markup inside the div with the id of app :

     <div id="app">
            <div class="container">
                <h4>Drag and Drop here</h4>
            </div>
            {{message}}
        </div>

And then add this styles in the head tag:

     <style>
            .container {
                width: 350px;
                height: 350px;
                border: 2px dotted gray
            }
            .container h4 {
                text-align: center;
                font-family: sans-serif;
            }
        </style>

After doing this you will have this result:

Vuejs Drag and Drop

Add data property

We now have to add a data property that will hold our files that has been dropped on the box. To do that add below to the data property in the Vue instance:

 files: [],

After that we will add a @drop event that will select our files and also a v-cloak atrribute that is used in hiding {{tags}} before app load.

Now our div should look like this:

 <div class="container" v-cloak @drop.prevent="addFile" @dragover.prevent>
    <h4>Drag and Drop here</h4>
 </div>

We need to define the addFile method in our Vue instance. To do this we will create a methods object in the Vue instance that will hold all our Vuejs methods:

 addFile(e) {
      let files = e.dataTransfer.files;
      [...files].forEach(file => {
        this.files.push(file);
        console.log(this.files)
      });
    }

After doing this, Open up your console and try dragging and dropping a file inside the box. Doing this will log the file details inside the box.

What we can do is display the selected images inside the box using the <li> tag. Let's add that feature by modifying the codes to this:

     <div class="container" v-cloak @drop.prevent="addFile" @dragover.prevent>
        <h4>Drag and Drop here</h4>
        <li v-for="(file,id) in files" :key="id" class="list-group-item mb-3 border-top">
        {{ file.name }} ({{ file.size }} kb)
        <button>Remove</button>
     </div>

Now if you drag and drop a file, You will get the file name and the file size.

Remove images from Vuejs Drag and Drop

We can also add a method that will remove a file from the files array by adding a method to the remove button:

<button @click="removeFile(file)">Remove</button>

And then create the removeFile method inside the methods object:

 removeFile(file) {
      this.files = this.files.filter(f => {
        return f != file;
      });
    },

With this, You can now remove any file from the files array.

Lets go extra step by creating a Vuejs filter that will format the side of each file. Create a filter object and add this method:

 filters: {
    kb(val) {
      return Math.floor(val / 1024);
    }
  },

Basically what this will do is divide the size of our file by 1024 to get the actually size. To use a Vuejs filter you have to pass a pipe to use it by doing this:

    {{ file.name }} ({{ file.size | kb }} kb)

Vue Drag and Drop

Styling up our Vue Drag and Drop with Bootstrap

To make our user interface look better, we can add the bootstrap CSS CDN and also google fonts into our application. Let modify our HTML head to this:

 <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Drag and Drop</title>
    <link
      href="https://fonts.googleapis.com/css2?family=Kumbh+Sans&display=swap"
      rel="stylesheet"
    />
    <link
      rel="stylesheet"
      href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css"
      integrity="sha384-JcKb8q3iqJ61gNV9KGb8thSsNjpSL0n8PARn9HuZOnIxN0hoP+VmmDGMN5t9UJ0Z"
      crossorigin="anonymous"
    />
    <script src="https://cdn.jsdelivr.net/npm/vue"></script>
    <style>
      * {
        font-family: "Kumbh Sans", sans-serif;
      }
      .wrapper {
        width: 350px;
        height: 350px;
        border: 2px dotted gray;
      }
    </style>
  </head>

With this added we can now modify our markup to this:

     <body>
        <div id="app">
          <nav class="navbar navbar-light bg-info">
            <div class="container">
              <a class="navbar-brand" href="#">Vue Drag and Drop</a>
            </div>
          </nav>
          <div class="container">
            <div class="row mt-4">
              <div class="col-md-6 offset-md-3">
                <div
                  class="wrapper px-2"
                  v-cloak
                  @drop.prevent="addFile"
                  @dragover.prevent
                >
                  <h4 class="mt-3 text-center">Drag and Drop here</h4>
                  <ul class="list-group">
                    <li class="list-group-item" v-for="(file,id) in files">
                      {{ file.name }} ({{ file.size | kb }} kb)
                      <button
                        class="btn btn-danger btn-sm float-right"
                        @click="removeFile(file)"
                      >
                        x
                      </button>
                    </li>
                  </ul>
                </div>
              </div>
            </div>
          </div>
        </div>
        <script src=" main.js"></script>
      </body>

Now your application should look like this:

Drag and Drop

Posted on by:

suniljoshi19 profile

Sunil Joshi

@suniljoshi19

An avid designer cum developer who is passionate about solving complex UX challenges across digital businesses.

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