Vue Smooth Height (VSM)

A Vue mixin that answers the question, "How do I transition height: auto?"

When the component's data is changed (i.e. when the updated lifecycle hook is called), its current height will smoothly transition to the new height, instead of instantly resizing.

Note that this library has no overlap with Vue's built in transition components.

Demo

https://jsfiddle.net/axfwg1L0/94/

Installation

Download via npm:

$ npm install vue-smooth-height

Include via cdn:

<script src="https://unpkg.com/vue-smooth-height"></script>

Usage

Module:

<template>
    <div>
        <div ref="container"></div>
    </div>
</template>

<script>
import smoothHeight from 'vue-smooth-height';

export default {
    mixins:[smoothHeight],
    mounted(){
        this.$smoothElement({
            el: this.$refs.container,
        })
    },
}
</script>

Browser:

The mixin is available via the global variable SmoothHeight

Vue.component('myComponent', {
    mixins:[SmoothHeight],
    mounted(){
        this.$smoothElement({
            el: this.$refs.container,
        })
    },
     template:
        `
        <div>
            <div ref="container"></div>
        </div>
        `
})

Transitions

VSM will check if the element has a height transition, either through the stylesheet or inline styles. If it exists, VSM will use that. If it doesn't, it will apply transition: height .5s to the element's inline style, and append any existing transition properties it finds.

For example, if the element has this style:

.element {
    transition: opacity 1s;
}

VSM will set style="transition: opacity 1s, height .5s;" on the element during the transition. After the transition, it will remove the inline style.

For compatibility, do not set transitions on other properties as an inline style, as they will be overridden.

Child transitions

Oftentimes a child element will be removed with a vue transition, rather than immediately removed. This child transition will be detected, and the container height will be transitioned after it detects a bubbled transitionend event.

Beware of giving child elements a height transition, it'll conflict with this library's transition. If you feel the need to do so, you don't need VSM on the container element.

Interrupted transitions

If the transition is interrupted, it will transition from the interrupted height to the new height. You don't need to do anything.

API

$smoothElement(options)

options: Object | Array

Can be a single options object, or an array of options objects.

Enables smooth height transition on an element.

Option	Type	Default	Description
el	Element, String	The component's $el	A reference to the element, or a selector string. Use a selector string if the element is not rendered initially. If the selector string returns multiple elements, the first matched element will be used.
transition	String	height .5s	The CSS shorthand transition property. Use this option if you don't want to use stylesheets (<style>...</style>).
childTransitions	Boolean	true	Run height transition after child transitions finish.
hideOverflow	Boolean	false	If the element has overflow-y: auto, a scrollbar can temporarily appear during the transition. Set this option to true to hide the scrollbar during the transition.
debug	Boolean	false	Logs messages at certain times within the transition lifecycle.

$unsmoothElement(options)

options: Object | Array

Can be a single options object, or an array of options objects.

Disables smooth height behavior on an element. Registered elements that have the same el as the passed in options will be unregistered. This usually isn't necessary, but is useful if you want to disable the behavior while the component is still alive.

Examples:

mounted(){
    // Zero config. Enables smooth height on this.$el
    this.$smoothElement()
    // Register with element reference
    this.$smoothElement({
        el: this.$refs.container,
    })
    // Register with classname. The first match will be used.
    this.$smoothElement({
        el: '.container',
    })
    // Pass an array of options
    this.$smoothElement([
        {
            el: this.$refs.container,
        },
        {
            el: '.container',
            transition: 'height 1s ease-in-out .15s'
            hideOverflow: true,
            debug: true,
        }
    ])
    // If the element reference is a component,
    // make sure to pass in its "$el" property.
    this.$smoothElement({
        el: this.$refs.container.$el,
    })

},

Browser compatibility

Due to various browser quirks, I cannot guarantee that vue-smooth-height will work as intended on every browser.