After 20 version of 0.0.x, Forsteri is finally stable in and released 0.1.

Forsteri

Reusable reactive Web Component with Virtual DOM in 2KB (gzipped).

Inspiration

Virtual DOM has been introduced to Web Development for many year. The key take away is to update only neccessary thus lead a great step forward in web development.

Each library has it's own ecosystem and trying to make itself reusable. But the one take away is, they could only reuse in it's own environment which means working across multiple library on large-scale project is lock down.

While most library with Virtual DOM size are too large for many developer to tolerate. Forsteri is inspired by Preact of how small Virtual DOM could be.

But how could we make a component to be reusable and still gaining benefit from Virtual DOM? So just create one, a simple and light-weight one which connect each component across many libraries.

Reusable + Virtual DOM

Web Component, a native reusable component.
Virtual DOM, more performant and easier way to control DOM.

What if, we could have a benefit of both world while still easy-to-use and light-weight on it's own.

That's why Forsteri is created. To create a reusable Web Component with Virtual DOM while it is still easy to create and use.

Why?

Forsteri is a library which helps create high-performance web component.

Feature:

Reusable for every project.
Virtual DOM and JSX.
Simple way to create web component.
Reactive.
No class, just function.
Encapsulation, ensure how the component looks.
Expressive Vanilla like API structure.
Very fast and small. (1.8KB Gzipped)
First Class TypeScript support.
Zero Dependencies.

And how does the syntax looks like?

It's just as simple as

// Get utility
import { h, registerComponent } from 'forsteri'

// Define how component looks like
let view = () => <h1>Forsteri Element</h1>

// Create Component
registerComponent({
    component: 'my-element',
    view
})

And add my-element to HTML.

<body>
    <my-element></my-element>
</body>

Performance

Forsteri use Virtual DOM to compare the difference between DOM. This proven has better performance than rewrite the whole DOM node and re-create one by one.

Forsteri is optimized for effective DOM manipulation. Contrast to React, Forsteri use diffing algorithms betweeen two object instead of an actual DOM node. Which is significantly faster.

As the component splited into multiple component and landed on each node. The component itself could never diff into the other, means it only diff and end in itself instead of finding the difference from the whole page.

This powered Forsteri to be very fast and remove unnecessary algorithms to find difference between each component.

Getting Started

Glad you're interested in Forsteri! Let's take a quick start with a starter template which has a perfect configured environment.

git clone https://github.com/SaltyAom/forsteri-typescript-starter

The starter template has a suitable environment to start trying a web component.

You can also see how the starter template looks like on this demo.

Including:

Configured JSX, using HTML syntax in JavaScript
Development environment and production built.
Minimal Starter suitable for higher integration.
TypeScript built-in.

Or setting up your own development environment

Start by installing Forsteri

yarn add forsteri

JSX and HyperScript

Let's start by exploring code structure, enviroment and how it work.

It's all start by defining a Function Component with determined how should it's looks like. If you're familiar with React, it's almost the same like how you define in React.

// Get utility
import { h } from 'forsteri'

// Define how component looks like
let view = () => <h1>Forsteri Element</h1>

But how and why does HTML are in JavaScript!?

By writing a simple <h1>Forsteri Element</h1>, it was translated to:

h('h1', null, 'Forsteri Element')

This is called JSX. Which introduced to React and widely used in React, Vue and others Virtual DOM library.

By defining a HTML structured like is far easier than how define view in JavaScript. A simple HTML contains a complex JavaScript structured

<section id="card">
    <h1 class="title" style="font-size: 1.5em">
        Hello World
    </h1>
</section>

Which translated to

h(
    'section',
    {
        id: 'card'
    },
    h(
        'h1',
        {
            class: 'title',
            style: {
                fontSize: '1.5em'
            }
        },
        'Hello World'
    )
)

An imported h is a shorten for HyperScript which inspired the way how Virtual DOM structured. We use defined an element in Virtual DOM, a function for element-creation is mandatory. That's why we included h for every component which has Virtual DOM defined.

Which means this work:

import { h } from 'forsteri'

const Card = () => <h1>Hello World</h1>

But this doesn't work:

const Card = () => <h1>Hello World</h1>

By default, Forsteri use babel-plugin-react-jsx and define pragma with babel-plugin-jsx-pragmatic to convert JSX to Forsteri's HyperScript. Which power JSX of Forsteri DOM creation.

Function Component

Forsteri is inspired by React's Function Component. Defining a simple function which contains logical expression.

const Card = <
    StateType extends Object,
    PropsType extends string[] as const
>(
    stateObject: State<StateType> {
        state: StateType,
        set: (
            key: keyof StateType,
            value: StateType[keyof StateType]
        ) => StateType
    },
    props: Record<PropsType[number], string>)
) => ForsteriVNode

Which can be typed like this in TypeScript:

import { h, ForsteriComponent } from 'forsteri'

const state = { message: 'Hello World' },
    props = ['title'],
    View: ForsteriComponent<typeof state, typeof props> = (
        { state: { message }, set },
        { title }
    ) => {
        return <h1>Hello World</h1>
    }

We'll discussed about state and props later.

In basic way it's looks like

const View = () => <h1>Hello World</h1>

You could write view like how you write in HTML. Forsteri use native attributes contrast to React. Which means you doesn't have to use className instead of class.

Register Component

registerComponent() is a function which define how component should represented to browser. How should it's tag looks like, how should it render, what should it contains?

It receive these following parameter:

registerComponent({
    component: string,         // Define component's name
    view: ForsteriComponent,   // Function component which we declared
    state?: State<StateType>,  // State
    props?: Props<PropsType>   // Props
})

In most basic way its important part is:

const Card = () => <h1>Hello World</h1>

registerComponent({
    component: 'my-element',
    view: Card
})

State

Like Angular, React and Vue, Forsteri also has state.
State is a variable which responsible for storing data and display it to the view.

When it the state changed, the it suddenly reflect to the view, update only its part.

To define a state, we defining it in plain object with its initial value.

let state = {
    message: 'Hello World'
}

And add it to registerComponent:

registerComponent({
    component: 'my-element',
    view: Card
})

Then function component will receive the state with helpers as its first parameters.

const Card = (state) => <h1>Hello World</h1>

// state
{
    state: {
        message: 'Hello World'
    },
    set: (stateName, newValue) => newValue
}

We destruct these state to 2 types: state and set.

state - contains object represent state.
set - function which receive state name and its new value.

Display to view

Then we display its value to the view by object destructing:

const Card = ({ state: {  message } }) => <h1>{message}</h1>

And then when we added <my-element> to HTML, it would display:

<h1>Hello World</h1>

Update state

In real-world, state change very often as its designed to be. State is a variable which change often.

Let's say we create a counter. Every time we click a button, a counter is increased, but how would we do it? We use set(), a helper function to update state.

First, let's define a view and state.

import { h, registerComponent } from 'forsteri'

const state = {
        counter: 0
    },
    Counter = ({ state: { counter }, set }) => (
        <section>
            <h1>{counter}</h1>
            <button>Increase</button>
        </section>
    )

registerComponent({
    component: 'my-counter',
    view: Counter
})

Notice that we have set here, it is responsible to update state and reflect to view.

To update state, we simply need state name and it's new value:

set('counter', counter + 1)

By default state is immutable object, we can't directly update it's value. Which we have set() to update its value.

Then we attach event and invoke set().

<section>
    <h1>{counter}</h1>
    <button onClick={() => set('counter', counter + 1)>Increase</button>
</section>

In result this is how we looks like:

import { h, registerComponent } from 'forsteri'

const state = {
        counter: 0
    },
    Counter = ({
        state: { counter },
        set
    }) => (
        <section>
            <h1>{counter}</h1>
            <button
            	onClick={() => set('counter', counter + 1)}
            >
                Increase
            </button>
        </section>
    )

registerComponent({
    component: 'my-counter',
    view: Counter
})

In action

Now every time we click the button, it's counter would increase by one.

Props

Contrast to state, it's super simple. props is shorten for properties. A property is like a HTML attribute. For a button like:

<button class="nice-button">Hello! I'm a button</button>

Class is a props of this button and it's value is "nice-button".

Like state, and defined props and add to registerComponent() but in contrast, we only need to define it's name as a string of array.

let props = ['class']

registerComponent({
    component: 'my-card',
    view: Card,
    props
})

Function Component get props as second parameter as an object:

const Card = (_, props) => <section></section>

We can use object destructing to get it's value:

const Card = (_, { class }) => (
    <section class={class}></section>
)

Its props would get when added to our Web Component:

<my-card class="card"></my-card>

// Our component return: <section class="card"}></section>

Conditional Rendering

We could determined and control how our view looks like based on state and props

Let's say on previous counter element, we would like to hide it's increase button.

We simply use if else to determined the view:

import { h, registerComponent } from 'forsteri'

const state = {
        counter: 0
    },
    Counter = ({ state: { counter }, set }) => {
        if (counter >= 10)
            return (
                <section>
                    <h1>{counter}</h1>
                </section>
            )

        return (
            <section>
                <h1>{counter}</h1>
                <button onClick={() => set('counter', counter + 1)}>
                    Increase
                </button>
            </section>
        )
    }

registerComponent({
    component: 'my-counter',
    view: Counter
})

Or better, we could use ternary operator to determined inline JSX.

import { h, registerComponent } from 'forsteri'

const state = {
        counter: 0
    },
    Counter = ({ state: { counter }, set }) => (
        <section>
            <h1>{counter}</h1>
            {counter >= 10 ? (
                <fragment />
            ) : (
                <button onClick={() => set('counter', counter + 1)}>
                    Increase
                </button>
            )}
        </section>
    )

registerComponent({
    component: 'my-counter',
    view: Counter
})

After counter is more or equal to 10, it's button should disappear.

You can also use props to determined how component looks like, but keep in mind that props isn't be able to change by itself. Only its parent should change it's props.

Fragment

In JSX, we couldn't simply return multiple element in one root node due to an Virtual DOM algorithm. But as an alternate way, we have fragment which represent a blank node which contains multiple node.

This fragment doesn't render to the view but its children is render instead. Without any children, it's render nothing.

// Render nothing
let View = () => <fragment />

// Normally we couldn't have multiple root node.
// With fragment, we could render multiple root node.
let Card = () (
    <fragment>
        <div>Hello World</div>
        <button>Nice Button</button>
    </fragment>
)

Children

Children is the most basic concept in HTML.

<my-card>
    <h1>Hello World</h1>
</my-card>

let Card = () <children />

This will render <my-card /> with <h1>Hello World</h1> inside.

When Children is rendered, it will become static skip the diffing algorithms when children is found, but as the children moved, to whole child node will be rewritten thus converting an unpredictable node is unefficient as the children designed to not be changed very often and shallow.

If wanted a complex children inside Forsteri Element while still have a Virtual DOM. You can defined a new Forsteri Element as a children of another Forsteri Element. This will ensure that Children as Virtual DOM.

As the child goes static, it's best practice to make sure vNode with the same level might become static. It's recommended to place children as an isolated child

// Do this
let Card = () => {
    <main>
        <h1>Hello World</h1>
        <section>
            <children />
        </section>
    </main>
}

// Not this
let Card = () => {
    <main>
        <h1>Hello World</h1>
        <children />
    </main>
}

Encapsulation

Shadow DOM is used to encapsulate logic and style. Preventing an unexpected change while working in multiple library.

External stylesheet wouldn't affected content inside Shadow DOM which also applied to our web component.

// style.css
h1 {
    color: red;
}

// index.html
<link rel='stylesheet' href='style.css'>
<my-card></my-card>

// card.tsx
let Card = () => <h1>Title</h1> // Doesn't affected by style.css

To use external stylesheet in Forsteri Component, you can assign stylesheet in a component instead.

let Card = () => (
    <fragment>
        <link rel='stylesheet' href='style.css'>
        <h1>Title</h1> // Affected by style.css
    </fragment>
)

To make sure our component keeps as same as should looks like. It only displayed when every stylesheet its required loaded.

That's pretty all important concept of Forsteri.

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

The stable released one