fork

this is a fork of https://github.com/Akryum/vue-observe-visibility to fix this.observer is null bug.

vue-observe-visibility

Detect when an element is becoming visible or hidden on the page.

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Table of contents

• Installation
• Usage
• Example

Installation

npm install --save vue-observe-visibility

⚠️ This plugin uses the Intersection Observer API that is not supported in every browser (currently supported in Edge, Firefox and Chrome). You need to include a polyfill to make it work on incompatible browsers.

Import

import Vue from 'vue'
import VueObserveVisibility from 'vue-observe-visibility'

Vue.use(VueObserveVisibility)

Or:

import Vue from 'vue'
import { ObserveVisibility } from 'vue-observe-visibility'

Vue.directive('observe-visibility', ObserveVisibility)

Browser

<script src="vue.js"></script>
<script src="vue-observe-visibility/dist/vue-observe-visibility.min.js"></script>

The plugin should be auto-installed. If not, you can install it manually with the instructions below.

Install all the directives:

Vue.use(VueObserveVisibility)

Use specific directives:

Vue.directive('observe-visibility', VueObserveVisibility.ObserveVisibility)

Usage

The v-observe-visibility directive is very easy to use. Just pass a function as the value:

<div v-observe-visibility="visibilityChanged">

This also works on components:

<MyComponent v-observe-visibility="visibilityChanged" />

The function will be called whenever the visiblity of the element changes with the argument being a boolean (true means the element is visible on the page, false means that it is not).

The second argument is the corresponding IntersectionObserverEntry object.

visibilityChanged (isVisible, entry) {
  this.isVisible = isVisible
  console.log(entry)
}

IntersectionObserver options

It's possible to pass the IntersectionObserver options object using the intersection attribute:

<div v-observe-visibility="{
  callback: visibilityChanged,
  intersection: {
    root: ...,
    rootMargin: ...,
    threshold: 0.3,
  },
}">

Once

It can be useful to listen for when the element is visible only once, for example to build introduction animations. Set the once option to true:

<div v-observe-visibility="{
  callback: visibilityChanged,
  once: true,
}">

Throttling visibility

You can use the throttle options (in ms) specifying minimal state duration after which an event will be fired. It's useful when you are tracking visibility while scrolling and don't want events from fastly scrolled out elements.

<div v-observe-visibility="{
  callback: visibilityChanged,
  throttle: 300,
}">

Passing custom arguments

You can add custom argument by using an intermediate function:

<div v-observe-visibility="(isVisible, entry) => visibilityChanged(isVisible, entry, customArgument)">

Here visibilityChanged will be call with a third custom argument customArgument.

Example

<div id="app">
  <button @click="show = !show">Toggle</button>
  <label>
    <input type="checkbox" v-model="isVisible" disabled/> Is visible?
  </label>
  <div ref="test" v-show="show" v-observe-visibility="visibilityChanged">Hello world!</div>
</div>

<script>
new Vue({
  el: '#app',
  data: {
    show: true,
    isVisible: true,
  },
  methods: {
    visibilityChanged (isVisible, entry) {
      this.isVisible = isVisible
      console.log(entry)
    },
  },
})
</script>

License

MIT