Snabbdom

A virtual DOM library with focus on simplicity, modularity, powerful features and performance.

Note: Snabbdom is mostly done. I'm currently only making minor tweaks. The documentation however is still quite lagging.

Table of contents

• Introduction
• Features
• Inline example
• Examples
• Core documentation
• Modules documentation

Why

Virtual DOM is awesome. It allow us to express our applications view as a function of its state. But existing solutions where way way too bloated, too slow, lacked features, had an API biased towards OOP and/or lacked features I needed.

Introduction

Snabbdom consists of an extremely simple, performant and extensible core that is only ≈ 200 SLOC. It offers a modular architecture with rich functionality for extensions through custom modules. To keep the core simple all non-esential functionality is delegated to modules.

You can mold Snabbdom into whatever you desire! Pick, choose and customize the functionality you want. Alternatively you can just use the default extensions and get a virtual DOM library with high performance, small size and all the features listed below.

Features

• Core features
  • About 200 SLOC – you could easily read through the entire core and fully understand how it works.
  • Extendable through modules.
  • A rich set of hooks available both per vnode and globally for modules so they can hook into any part of the diff and patch process.
  • Splendid performance. Snabbdom is among the fastest virtual DOM libraries in the Virtual DOM Benchmark.
  • Patch function with a function signature equivelant to a reduce/scan function. Allows for easier integration with a FRP library.
• Features in modules
  • Features for doing complex animations.
  • Powerful event listener functionality
  • Thunks to optimize the diff and patch process even further

Inline example

var snabbdom = require('snabbdom');
var patch = snabbdom.init([ // Init patch function with choosen modules
  require('snabbdom/modules/class'), // makes it easy to toggle classes
  require('snabbdom/modules/props'), // for setting properties on DOM elements
  require('snabbdom/modules/style'), // handles styling on elements with support for animations
  require('snabbdom/modules/eventlisteners'), // attaches event listeners
]);
var h = require('snabbdom/h'); // helper function for creating VNodes
var vnode = h('div#id.two.classes', {on: {click: someFn}}, [
  h('span', {style: {fontWeight: 'bold'}}, 'This is bold'),
  ' and this is just normal text',
  h('a', {props: {href: '/foo'}, 'I\'ll take you places!'})
]);
var container = document.getElementById('container');
// Patch into empty DOM element – this modifies the DOM as a side effect
patch(container, vnode);

Examples

• Animated reordering of elements
• Hero transitions

Core documentation

The core of Snabbdom provides only the most essential functionality. It is designed to be as simple as possible while still being fast and extendable.

snabbdom.init

The core exposes only one single function snabbdom.init. init takes a list of modules and returns a patch function that uses the specified set of modules.

var patch = snabbdom.init([
  require('snabbdom/modules/class'),
  require('snabbdom/modules/style'),
]);

patch

The patch function returned by init takes two arguments. The first is a DOM element or a vnode representing the current view. The second is a vnode representing the new view.

patch(oldVnode, newVnode);

snabbdom/h

It is recommended that you use snabbdom/h to create VNodes. h accepts a a tag/selector as a string, an optional data object and an option string or array of children.

var h = require('snabbdom/h');
var vnode = h('div', {style: {color: '#000'}}, [
  h('h1', 'Headline'),
  h('p', 'A paragraph'),
]);

Hooks

Name	Triggered when	Arguments to callback
pre	the patch process begins.
create	a DOM element has been created based on a VNode.	emptyVNode, createdVnode
insert	an element has been inserted into the DOM.	insertedVnode
patch	an element is about to be patched.	oldVnode, newVnode
update	an element is being updated.	oldVnode, newVnode
remove	an element is directly being removed from the DOM.	vnode, removeCallback
destroy	an element is begin removed from the DOM or it's parent is.	vnode
post	the patch process is done.

Modules documentation

This describes the core modules.

The class module

The class module provides an easy way to dynamically toggle classes on elements. It expects an object in the class data property. The object should map class names to booleans that indicates whether or not the class should stay or go on the VNode.

h('a', {class: {active: true, selected: false}}, 'Toggle');

The props module

Allows you to set properties on DOM elements.

h('a', {props: {href: '/foo'}, 'Go to Foo');

The style module

The style module is for making your HTML look slick and animate smoothly. At it's core it allows you to set CSS properties on elements.

h('span', {
  style: {border: '1px solid #bada55', color: '#c0ffee', fontWeight: 'bold'}
}, 'Say my name, and every colour illuminates');

Delayed properties

You can specify properties as being delayed. Whenver these properties change the change is not applied until after the next frame.

h('span', {
  style: {opacity: '0', transitionDuration: 'opacity 1s', delayed: {opacity: '1'}}
}, 'Imma fade right in!');

Set properties on remove

h('span', {
  style: {opacity: '1', transitionDuration: 'opacity 1s',
          remove: {opacity: '1'}}
}, 'It\'s better to fade out than to burn away');

Set properties on destroy

h('span', {
  style: {opacity: '1', transitionDuration: 'opacity 1s',
          destroy: {opacity: '1'}}
}, 'It\'s better to fade out than to burn away');

Eventlisteners module

The event listeners module gives powerful capabilities for attaching event listeners.

You can attach a function that will be called with the event object.

function clickHandler(ev) { console.log('got clicked'); }
h('div', {on: {click: clickHandler}});

We can also use the array syntax to attach a function that will be invoked with a constant value.

function clickHandler(number) { console.log('button ' + number + ' was clicked!'); }
h('div', [
  h('a', {on: {click: [clickHandler, 1]}}),
  h('a', {on: {click: [clickHandler, 2]}}),
  h('a', {on: {click: [clickHandler, 3]}}),
]);