Affixes an element on the screen while you scroll

This vue 2 component will act kinda like Bootstrap's Affix plugin, but in a simpler and smarter way.

• Affixes your element as you scroll
• No dependencies
• Only needs 3 super simple configuration steps
• Dispatch events when the affix class changes
• Vue2
• Uses pure JS!

Check the demo!

Installation

Install via npm and use it as a vue plugin in your app.

npm install --save-dev vue-affix

var Affix = require('vue-affix');
Vue.use(Affix);

Usage

• Wrap the element in an <affix> tag
• Set an element selector in a relative-element-selector property
• Set a width value for the .vue-affix class in your CSS (that is the element which the affix will be applied to)

Example below:

<affix class="sidebar" relative-element-selector="#home">
    <a href="#home">Home</a>
    <a href="#about-us">About Us</a>
    <a href="#portfolio">Portfolio</a>
    <a href="#contact">Contact</a>
</affix>
<section id="home" class="section">
    <p>This is the #home section which the sidebar will be relatively affixed!</p>
</section>

This will make the .sidebar element stay fixed while in the #home element viewport. Simple as that.

Events

vue-affix will dispatch 3 different events:

• affixtop will be dispatched when the .affix-top class is applied, that is when you scroll above the relative element.
• affix will be dispatched when the .affix class is applied, that is while you scroll inside the relative element.
• affixbottom will be dispatched when the .affix-bottom class is applied, that is when you scroll below the relative element.

Those can be catched as I show in the example below:

<affix class="sidebar" relative-element-selector="#home" v-on:affixbottom="yourFunction()">
    <a href="#home">Home</a>
    <a href="#about-us">About Us</a>
    <a href="#portfolio">Portfolio</a>
    <a href="#contact">Contact</a>
</affix>

How the plugin works

It works similar to Bootstrap's Affix plugin, it will add 3 classes (.affix-top, .affix and .affix-bottom) to the element to affix while you scroll the page.

Unlike Bootstrap's Affix, all you need to do in vue-affix is set a width value for the class .vue-affix (that's because when the position: fixed property is applied, it will lose it's relative width value) and add an element in the relative-element-selector property.

vue-affix will calculate when to start/stop affixing relatively to the element you provide in the relative-element-selector property, that means you don't have to do any calculation, just set the relative element and that will be all done automatically.

You can also set an offset object with the top and bottom values that will be used as a threshold to start/stop affixing the element, but that is optional.

Configuration

The only configuration you need to do in CSS is setting a width for the .vue-affix class, the rest will be applied through props as in the example below:

<affix class="sidebar" relative-element-selector="#home" :offset="{ top: 40, bottom: 40}">
    <a href="#home">Home</a>
    <a href="#about-us">About Us</a>
    <a href="#portfolio">Portfolio</a>
    <a href="#contact">Contact</a>
</affix>

Props

/**
 * The relative element selector string. The relative element is
 * the element you want your affix to be related to, as it will
 * not be related to the window.
 *
 * @example '#contact'
 * @type {String}
 */
relativeElementSelector: {
    type: String,
    required: true
},

/**
 * This is the offset margin between the top/bottom of the window
 * before the affix is applied.
 *
 * @type {Object}
 */
offset: {
    type: Object,
    default: () => {
        return {
            top: 40,
            bottom: 40
        }
    }
}