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vue-observe-visibility

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

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## Table of contents - [Installation](#installation) - [Usage](#usage) - [Example](#example) # Installation ``` npm install --save vue-observe-visibility ``` **⚠️ This plugin uses the [Intersection Observer API](http://caniuse.com/#feat=intersectionobserver) that is not supported in every browser (currently supported in Edge, Firefox and Chrome). You need to include a [polyfill](https://github.com/w3c/IntersectionObserver/tree/master/polyfill) to make it work on incompatible browsers.** ## Import ```javascript import Vue from 'vue' import VueObserveVisibility from 'vue-observe-visibility' Vue.use(VueObserveVisibility) ``` Or: ```javascript import Vue from 'vue' import { ObserveVisibility } from 'vue-observe-visibility' Vue.directive('observe-visibility', ObserveVisibility) ``` ## Browser ```html ``` The plugin should be auto-installed. If not, you can install it manually with the instructions below. Install all the directives: ```javascript Vue.use(VueObserveVisibility) ``` Use specific directives: ```javascript Vue.directive('observe-visibility', VueObserveVisibility.ObserveVisibility) ``` # Usage The `v-observe-visibility` directive is very easy to use. Just pass a function as the value: ```html
``` This also works on components: ```html ``` 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](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserverEntry) object. ```javascript visibilityChanged (isVisible, entry) { this.isVisible = isVisible console.log(entry) } ``` ## IntersectionObserver options It's possible to pass the [IntersectionObserver `options` object](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/IntersectionObserver#Parameters) using the `intersection` attribute: ```html
``` ## 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`: ```html
``` ## 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. ```html
``` You can also pass a `leading` option to trigger the callback the first time when the visibility changes without waiting for the throttle delay. I can either be `visible`, `hidden` or `both`. ```html
``` ## Passing custom arguments You can add custom argument by using an intermediate function: ```html
``` Here `visibilityChanged` will be call with a third custom argument `customArgument`. ## Disabling the observer Passing a falsy value to the directive will disable the observer: ```html
``` # Example ```html
Hello world!
``` --- ## License [MIT](http://opensource.org/licenses/MIT)