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Write Snabbdom virtual DOM with
Babel's JSX.
Snabbdom is a small Virtual DOM library. Unlike React, it's not a full View
framework, it just focuses on the core virtual DOM problem : construct virtual DOM
trees (virtual nodes) and patch the real DOM with them. it's entirely up to you
to decide when those operations will happen. The main benefit is that you can adopt
whatever architectural UI pattern you like in your application.
Babel is a JavaScript compiler that converts modern JavaScript (ES2015 and beyond)
into compatible JavaScript (ES5) code. A nice feature of Babel is that it supports
React JSX syntax and
in the same time allows you to take the result of this JSX (attributes + body) and do
whatever you like with it. Snabbdom-jsx transforms this JSX data into Snabbdom virtual nodes.
Features:
- Transforms Babel JSX templates into Snabbdom virtual nodes
- Straightforward mapping from JSX attributes to Snabbdom data attributes using namespaces
- JSX Components are simple functions
(attributes, children) => vnode
. No more messy classes.
Usage
installation
npm install snabbdom-jsx
Hello example (see the complete example here)
import { html } from 'snabbdom-jsx';
const patch = snabbdom.init([...]);
const vnode = <div>Hello JSX</div>
patch(document.getElementById('placeholder'), vnode);
The /** @jsx html */
pragma at the top tells Babel to use the html
function instead
of the React.createElement default. The html
function takes arguments passed from Babel
and generates virtual nodes as expected by Snabbdom's patch
function.
Mapping JSX attributes
A quick reminder: in snabbdom, most of the functionality like toggling classes, styles
and setting properties on DOM elements is delegated to separate modules.
For example
const myInput = h('input', {
props: { type: 'text' }
on: { change: someCallback },
class: { class1: isEnabled }
...
})
Each module handles a portion of the data attributes (the 2nd parameter to h
). And
each portion is stored inside a namespace, for example, event attributes are placed
inside the on
namespace, class attributes inside the class
namespace and so on.
By default all attributes listed in the JSX element are placed inside the props
namespace.
<input type="text" />
Is equivalent to
h('input', { props: { type: 'text' } })
To attach event listeners, we use the on-
prefix
<button on-click={ callback } />
h('button', { on: { click: callback } })
This is a generic rule to map a JSX attribute to a specific module, you need to prefix
the attribute with pref-
where pref
is the namespace used by the module in Snabbdom.
As in the example above, all attributes with the on-
prefix (i.e. event listeners) will
be placed inside the the on
namespace. This gives us a simple and extensible pattern to
support other custom modules.
Another example using the class
namespace
<div
class-visible={isVisible}
class-enabled={isEnabled}>
...
</div>
h('div', {
class: { visible: isVisible, enabled: isEnabled }
}, [...])
But you can also specify an unique object the same way as in the h
function, this is
useful when you have a dynamic object
<div
style={ ({fontWeight: 'bold', color: 'red'}) }>
...
</div>
h('div', {
style: {fontWeight: 'bold', color: 'red'}
}, [...])
You can mix both styles, the result will be a merge of all attributes
<div
class={ ({visible: isVisible}) }
class-enabled={isEnabled}>
...
</div>
Id and static classes (sel attribute)
In Snabbdom you can create an element using a css-like syntax
h('div#id.class1.class2', ...)
This will set the element id add the class names to its classList property. Unlike
classes specified in the class
namespace, those are static classes meaning they
will not be re-updated during patch operations.
In JSX you can use the selector
attribute to set the element's id and add static classes
<div selector="#id.class1.class2" />
You can also specify static classes via the classNames
property
<div classNames="class1 class2" />
You can also provide an array to classNames
instead of a string
const classes = ['class1', 'class2'];
<div classNames={classes} />
it's important to remember to not pass dynamic values to selector
or classNames
.
As this can lead to some unexpected issues. If you want to set dynamic classes, use
the class module instead.
JSX Components
In React/JSX you can create components and use them inside other components
var HelloMessage = React.createClass({
render: function() {
return <div>Hello {this.props.name}</div>;
}
});
React.render(<HelloMessage name="John" />, mountNode);
Instead of classes, Snabbdom-jsx components are simple functions of type
(attributes, children) => vnode
.
const HelloMessage = ({name}) =>
<div on-click={ _ => alert('Hi ' + name) }>
{name}
</div>;
var vnode = <HelloMessage name="Yassine" />
As in React, note that all components must start with a capital letter, while regular
HTML tags start with lower case letters. This the way Babel also distinguish component
invocation from simple tag creation.
Perhaps of less obvious utility, but instead of a function, a component can also be an
object with a view
or render
function. I added this in order to support nesting in
UI patterns; especially in the Elm architecture, where a component is an object with a
view
(or render
) function (among others)
for example you can have a Task
component
Task.view = ({task}) => ...
Task.update = ...
and use it inside a Todos
component like this
import Task from './task'
Todos.view = ({todos}) => todos.map(todo =>
<Task todo={todo} key={todo.id} />)
As illustrated above, you can also add a key
attribute directly to a Component.
It will be copied inside the resulting vnode
If you're wondering how Components would fit in a large application, you can look into
the todomvc example.
The application is implemented using the Elm architecture. For more information see
React-less Virtual DOM with Snabbdom : functions everywhere!