javascript - Load each item after the one before is finished loading in Vue JS - Stack Overflow

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I need to load around 1000 static images, .gifs, and videos for an online slideshow presentation. Currently all items are loading at once and viewers need to wait to see the first item. How to load each item after the one before is finished loading?

Vue.js Vuetify.js code:

<v-row v-for="(objkts, index) in group" :key="index">
   <v-col v-for="objkt in objkts" :key="objkt.id">
      <v-card :key="index" width="100vh">
         <v-img
            max-width="100vh"
            :src="img(objkt)"
            ></v-img>
      </v-card>
   </v-col>
</v-row>

I need to load around 1000 static images, .gifs, and videos for an online slideshow presentation. Currently all items are loading at once and viewers need to wait to see the first item. How to load each item after the one before is finished loading?

Vue.js Vuetify.js code:

<v-row v-for="(objkts, index) in group" :key="index">
   <v-col v-for="objkt in objkts" :key="objkt.id">
      <v-card :key="index" width="100vh">
         <v-img
            max-width="100vh"
            :src="img(objkt)"
            ></v-img>
      </v-card>
   </v-col>
</v-row>

• javascript
• performance
• vue.js
• vuetify.js
• preload

Share Improve this question Follow asked Oct 21, 2021 at 7:40 TomTom 6,0342121 gold badges8585 silver badges134134 bronze badges

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4 Answers 4

Sorted by: Reset to default 4

Solution:

Using an image list you need to dynamically set the src property on each image only when the previous image is loaded

Steps (5):

1. Create an array of image data with image URL stored in asrc property(you can name it anything).
2. Render each image from list using v-for directive.
3. Set image src to image.src instead of asrc

<img 
  v-for="(image,index) in group" :key="index"
  :src="image.src"

4. Also set an image load event to call loading of next image

<img 
  v-for="(image,index) in group" :key="index"
  :src="image.src"
  @load="loadNextimage(index)"/>

5. Whenever image loader is called then add src property to the image. This will start the image to load.

loadNextimage(currentIndex){
  let nextIndex = currentIndex+1
  if( nextIndex < this.group.length){
      let img = this.group[nextIndex]
      img.src = img.asrc
      delete img.asrc
     Vue.set(this.group, nextIndex, img)
  }
}

new Vue({
  el: '#app',
  data(){
  
    return {
      group: [
          { id: 1, title: '', asrc: 'https://source.unsplash./collection/190727/120x120'},
          { id: 2, title: '', asrc: 'https://source.unsplash./collection/8961198/120x120'},
          { id: 3, title: '', asrc: 'https://source.unsplash./collection/190723/120x120'},
          { id: 4, title: '', asrc: 'https://source.unsplash./collection/KizanWcExgU/120x120'}
      ]
    }
  },
  mounted(){
    this.loadNextimage(-1)
  },
  methods:{
    loadNextimage(currentIndex){
      let nextIndex = currentIndex+1
      if(nextIndex<this.group.length){
          let img = this.group[nextIndex]
          img.src = img.asrc
          delete img.asrc
         Vue.set(this.group,nextIndex,img)
      }
    }
  }
});

img {
    height: 120px;
    width:120px;
}

img:not([src]){
  background: url(https://www.slntechnologies./wp-content/uploads/2017/08/ef3-placeholder-image.jpg);
  background-size:cover;
}

<script src="https://cdnjs.cloudflare./ajax/libs/vue/2.5.17/vue.js"></script>
<script src="https://cdn.jsdelivr/npm/[email protected]/dist/vuetify.js"></script>

<div id="app">
    <img 
      v-for="(image,index) in group" :key="index"
      :src="image.src"
      @load="loadNextimage(index)"
    >
</div>

This is similar to Alphesh's solution but I think it's a little bit easier to read. The idea is to set up a simple queueing system with three properties:

1. imagesToLoad - The list of images/videos you need to load
2. loadingImage - The image that is currently loading
3. loadedImages - The images that have already loaded

You'll also have a simple method called queueNextImage which should be called by the mounted hook (to start the first image loading) and then again when an image is finished loading that looks like this:

queueNextImage() {
  if(this.loadingImage !== null) {
    this.loadedImages.push(this.loadingImage)
  }
  this.loadingImage = this.imagesToLoad.shift()
}

When you start imagesToLoad will be populated with all the image URLs you'd like to load and loadedImages will be an empty array.

The template will iterate through the loadedImages rendering them in a regular loop and will have a single img element having the src attribute bound to the value of loadingImage and which fires the queueNextImage from the onLoad event of the image.

Full example:

<template>
  <div>
    <p>
      Images to load: <span>{{imagesToLoad.length}}</span>
      Loading image: <span>{{loadingImage}}</span>
      Images Loaded: <span>{{loadedImages.length}}</span>
    </p>
    <img v-for="item in loadedImages" v-bind:key="item" v-bind:src="item" />
    <img v-on:load="queueNextImage" v-bind:src="loadingImage" />
  </div>
</template>

<script>
export default {
  mounted: function() {
    this.queueNextImage();
  },
  methods: {
    queueNextImage() {
      if(this.loadingImage !== null) {
        this.loadedImages.push(this.loadingImage)
      }
      this.loadingImage = this.imagesToLoad.shift()
    },
  },
  data: () => ({
    loadedImages: [],
    loadingImage: null,
    imagesToLoad: Array.from({length:200},(v,k)=>`https://via.placeholder./${k+850}`),
  }),
};
</script>

Try it on CodeSandbox.

You can use lazy ponent from vuetify: https://vuetifyjs./en/ponents/lazy/

Wrap your code inside this ponent and your html will be loaded based on visibility.

As far as I understand you want something like loading images one by one in the ascending order of the index.

You can try one approach like:

• Creating an async method and await the loading of the images in loop.

Pseudocode Example:

1. First replace the code in vue template

<v-img
    max-width="100vh"
    :src="imgCollection[index]"
></v-img>

2. Then load the images asynchronously one by one.

    async function loadImages() {
        imagesList.forEach((img, index) => {
            var data = await getImageData(img.url);
            
            // update the data into your array
            imgCollection[index] = data;
        });
    }

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