Is there a method in Vue to detect when rendering is complete?

Question

Is there a method in Vue to detect when rendering is complete?

I have experimented with the lifecycle hooks mounted and created, as well as using $nextTick within mounted, but none of them provide an accurate render when trying to access data from a DOM node after its initial render. Here's a snippet of my code:

mounted() {
  console.log(this.$el.getBoundingClientRect().top);
},

The above code gives me incorrect data. However, if I use this modified code:

mounted() {
  setTimeout(() => {
    console.log(this.$el.getBoundingClientRect().top);
  }, 1000)
},

With the modification, I get the correct data but there is a delay of approximately 700-900 ms before that happens.

Question 1

Why does the lifecycle hook trigger before everything has fully rendered?

Question 2

Could sibling components that haven't mounted yet be affecting dimensions and causing this issue?

Question 3

Is there an event or solution I can utilize to ensure that everything on the page has completely rendered?

I am not satisfied with the setTimeout workaround I currently have in place.

javascript vue.js vuejs2

Answer 1

Answer №1

Q1: When it comes to lifecycle hooks, the focus is solely on the instance itself rather than the entire DOM. This means that other parts of the page can be in a pending state while the component is fully mounted.

Q2: Similar to Q1.

Q3: One way to achieve this is:

document.addEventListener("DOMContentLoaded", function(event) {
    console.log(this.$el.getBoundingClientRect().top);
});

For a more detailed explanation: $(document).ready equivalent without jQuery

Edit

It's recommended to use this approach instead:

window.addEventListener("load", function(event) {
    console.log(this.$el.getBoundingClientRect().top);
});

I overlooked the aspect of external resources. DOMContentLoaded is triggered when the DOM is loaded (i.e., HTML), while load occurs after the external resources have been loaded. For further information: https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/onload

Answer 2

Q1: When it comes to lifecycle hooks, the focus is solely on the instance itself rather than the entire DOM. This means that other parts of the page can be in a pending state while the component is fully mounted.

Q2: Similar to Q1.

Q3: One way to achieve this is:

document.addEventListener("DOMContentLoaded", function(event) {
    console.log(this.$el.getBoundingClientRect().top);
});

For a more detailed explanation: $(document).ready equivalent without jQuery

Edit

It's recommended to use this approach instead:

window.addEventListener("load", function(event) {
    console.log(this.$el.getBoundingClientRect().top);
});

I overlooked the aspect of external resources. DOMContentLoaded is triggered when the DOM is loaded (i.e., HTML), while load occurs after the external resources have been loaded. For further information: https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/onload

Answer 3

Answer №2

Since elements are rendered asynchronously, it is difficult to guarantee that the position will remain consistent. It may be necessary to retrieve the position each time there is an update. This can be achieved using a custom directive, which triggers the update function when updates occur.

Check out this quick demonstration:

new Vue({
  el: '#app',
  data: {
    ht: 100,
    top: null
  },
  directives: {
    bounding(el, binding, vnode) {
      vnode.context[binding.expression] = el.getBoundingClientRect().top;
    }
  },
  mounted() {
    let times = 5;
    const i = setInterval(() => {
      this.ht += 10;
      if (--times < 1) {
        clearInterval(i);
      }
    }, 1000);
  }
});

<script src="//unpkg.com/vue@latest/dist/vue.js"></script>
<div id="app">
  <div :style="{height: `${ht}px`}">Hi</div>
  <div v-bounding="top">{{top}}</div>
</div>

Answer 4

Since elements are rendered asynchronously, it is difficult to guarantee that the position will remain consistent. It may be necessary to retrieve the position each time there is an update. This can be achieved using a custom directive, which triggers the update function when updates occur.

Check out this quick demonstration:

new Vue({
  el: '#app',
  data: {
    ht: 100,
    top: null
  },
  directives: {
    bounding(el, binding, vnode) {
      vnode.context[binding.expression] = el.getBoundingClientRect().top;
    }
  },
  mounted() {
    let times = 5;
    const i = setInterval(() => {
      this.ht += 10;
      if (--times < 1) {
        clearInterval(i);
      }
    }, 1000);
  }
});

<script src="//unpkg.com/vue@latest/dist/vue.js"></script>
<div id="app">
  <div :style="{height: `${ht}px`}">Hi</div>
  <div v-bounding="top">{{top}}</div>
</div>

Is there a method in Vue to detect when rendering is complete?

Question 1

Question 2

Question 3

Answer №1

Answer №2

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