animation of picture doesn't work! Vue.js

Question

The problem is when i am using set interval with this top: ${this.imgTop++}px !

const vue = require("@/assets/images/vue.png");
const bootstrap = require("@/assets/images/bootstrap.png");
const bulma = require("@/assets/images/bulma.png");

export default {
  name: "randImg",
  data() {
    return {
      images: [
        vue,
        bootstrap,
        bulma
      ],
      addedImage: [],
      imgTop: -100,
      imgLeft: -100,
      imgHeight: 64,
      imgWidth: 64,
      changeInterval: 750,
      selectedImage: ''
    }
  },
  created() {
    const randomImg = func => setInterval(func, this.changeInterval);
    randomImg(this.randomImage);
    randomImg(this.addImage);
    randomImg(this.randomPosition);
    setInterval(this.moveImage,50);
  },
  methods: {
    randomImage() {
      const idx = Math.floor(Math.random() * this.images.length);
      this.selectedImage = this.images[idx];
    },
    randomPosition() {
      const randomPos = twoSizes => Math.round(Math.random() * twoSizes);
      this.imgTop = randomPos(window.innerHeight - this.imgHeight);
      this.imgLeft = randomPos(window.innerWidth - this.imgWidth);
    },
    moveRandomImage() {
      const randomImg = func => setInterval(func, this.changeInterval);
      randomImg(this.moveImage);
      this.randomImage();
    },
    addImage() {
      this.addedImage.push({
        style: {
          top: `${this.imgTop}px`,
          left: `${this.imgLeft}px`,
          height: `${this.imgHeight}px`,
          width: `${this.imgWidth}px`
        },
        src: this.selectedImage
      });
    },
    moveImage() {
      this.addedImage.style = {
        style: {
          top: `${this.imgTop++}px`
        }
      }
    }
  }
}

don't understand why but this animataion doesnt work, basically i will explain how it works: every second i am adding new image with new position from addedImage: [] and i want this every picture to go down (top++)

additionally this is a template:

<div class="randImg">
    <img class="image" :style="image.style"
         :src="image.src"
         v-for="image in addedImage">
</div>

Answer 1

My guess it's possible to achieve what you want by adding a watcher on your addedImage array, like every time a new image element is added, you change the style.top of it.

But you shouldn't use nested setIntervals. I share you this answer explaining why.

---

I think a simpler and lighter solution is to use css, like creating a @keyframe translation rule:

.drop {
  animation: dropDown 1.5s ease-in forwards;
}

@for $i from 1 to 10 {
  .drop:nth-child(#{$i}) {
    animation-delay: $i * 1.5s;
    animation-duration: -1.5s;
  }
}

@keyframes dropDown {
  0% {
    transform: translateY(0);
  }
  100% {
    transform: translateY(600px);
    opacity: 0;
  }
}

Here's a live example

Answer 2

this.addedImage is an array of image, not an image. So, when you do this.addedImage.style , you add a style attribute to your array, but not to the images in the array.

Change moveImage for :

moveImage() {
  this.addedImage.forEach(image => {
    image.style.top = image.style.top + 1
  });
}