Components

Components encapsulate distinct pieces of UI functionality, promoting reusability, modularity, and ease of maintenance.

Anonymous component templates

The easiest way to define components in UIX is to use templates.

With anonymous component templates, you can still get behavior and stored states, but you don't get any advanced component features like lifecycle handlers and utility methods. Anonymous components are built on top of existing DOM API features (shadow roots, slots).

To define a new template, call the template function and pass in an element value (JSX definition) or a generator function that returns an element (JSX):

frontend/entrypoint.tsx
import { template } from "uix/html/template.ts";

// Define the template
const SimpleComponent = template(<div class="simple"/>);

// Instantiate the component
export default <SimpleComponent id="c1"/>;

will render as:

<div class="simple" id="c1"/>

The template method can also take properties (user defined attributes):

const ComplexComponent = template<{customAttr: number}>(({customAttr}) =>
    <div class="complex">
        <b>Answer is: {customAttr}</b>
    </div>
);

<ComplexComponent id="c2" customAttr={42}/>

will render as:

<div class="complex" id="c2">
    <b>Answer is: 42</b>
</div>

Child elements

Default element attributes (e.g. id and style) are assigned to the root element after it is created. Children defined in JSX are also appended to the root element by default:

const CustomComponent = template(<div class="class1"/>);

<CustomComponent id="c1">
    <div>Child 1</div>
    {'Child 2'}
</CustomComponent>

will be rendered as:

<div class="class1" id="c1">
    <div>Child 1</div>
    Child 2
</div>

Advanced example

const MyComponent = template<{
    background: 'red' | 'green',
    countstart: number
}>(({background, countstart}) => {
    // create a counter pointer
    const counter = $(countstart);

    // Increment the counter every second
    setInterval(() => counter.val++, 1000);

    // return component content
    return <div style={{background}}>
        Count: {counter}
    </div>;
});

<MyComponent background="green" countstart={42}>
    <div>Child 1</div>
    <div>Child 2</div>
</MyComponent>

Using blankTemplate / function components

For some use cases, it may be useful to access all attributes and the children set in JSX when creating an anonymous component.

The blankTemplate function allows you to create an element with complete control over attributes and children. Unlike template, children defined in JSX are not automatically appended to the root element of the template, and HTML attributes defined in JSX are not automatically set for the root element.

All attributes and children are available in the props argument of the generator function.

import { blankTemplate } from "uix/html/template.ts";

const CustomComponent = blankTemplate<{
    color:string
}>(({color, style, id, children}) => 
    <div id={id} style={style}>
        <h1 style={{color}}>Header</h1>
        {...children}
    </div>
);

<CustomComponent id="c1" color="blue">
    <div>First child</div>
    <div>Second child</div>
</CustomComponent>

This behavior is more similar to other JSX frameworks. You can also just use a normal function instead of blankTemplate (the blankTemplate is just a wrapper around a component function with some additional type features).

Keep in mind that UIX always returns the children property as an array, even if just a single child was provided in JSX.

function CustomFunctionComponent({color, id, children}: {id:string, children:JSX.Element[], color:string}) {
    return <div id={id} style={{color}}>
        {...children}
    </div>;
};

<CustomFunctionComponent id="c1" color="blue">
     <div>First child</div>
     <div>Second child</div>
</CustomFunctionComponent>

Custom class components

You can create custom UIX components by extending the Component class and registering it by decorating the class with @template.

import { template } from "uix/html/template.ts";
import { Component } from "uix/components/Component.ts";

// register the component and set default options
@template()
class MyCustomComponent extends Component {
    @content helloText = 'Hello from my custom component';
}

Class template components

Templates defined with template can also be used as a base layout for component classes - just use the template returned by template as a class decorator.

The simplest form is to use a static template definition by passing JSX directly to the template decorator:

@template(
    <article>
        <h1 id="header">UIX</h1>
        <section id="description">Hello, UIX!</section>
    </article>
)
class MyCustomComponent extends Component {
    public sayHello() {
        // Do something
    }
}

To allow for attributes to be handled in the template definition, it is recommended to use a template generator by passing a callback function that returns JSX to the template decorator:

@template(({title}) =>
    <article>
        <h1>{title}</h1>
        <section>Default section content</section>
    </article>
)
class MyCustomComponent extends Component<{
    title: string,
    additionalOption: number
}> {
    public sayHello() {
        // The passed parameters are available in 'properties'
        console.log(this.properties.title, this.properties.additionalOption);
    }
}

<MyCustomComponent title="Hello, UIX!" additionalOption={42}>

Custom attributes defined for your components (such as title and additionalOption in above example) can be accessed via the properties field. This acts as a type-safe accessor similar to props in React.

It is possible to use predefined templates to abstract behaviour:

const CoolDiv = template(<div>What is cooler than being cool?</div>);

@CoolDiv
class MyCustomComponent extends Component<{title:string}> {
    // ...
}

The @id decorator

With the @id decorator, component properties can be bound to the element inside the component that has an id attribute set that matches the properties name.

To access elements defined in the template layout consider assigning an unique id attribute to the corresponding elements:

@template(
    <div id="parent">
        <h1>Hello</h1>
        <input id="myInput" value="Hello, UIX!" type="text"/>
    </div>
)
class MyApp extends Component {
    // declare myInput automaticially since myInput property matches id
    @id myInput!: HTMLInputElement;

    // declare id explicitly if property name does not match id
    @id('parent') myParent!: HTMLDivElement;
}

Note that, when the property is overridden, the element with the matching id is also replaced with the new property.

Component lifecycle

Class components extending the Component class will expose methods to handle the components lifecyle.

@Component
class CustomComponent extends Component {
    // called when component is constructed
    onConstruct() {}

    // called after component is constructed or restored
    onInit() {}

    // called once before onAnchor
    onCreate() {}

    // called every time the component is added to a new parent in the DOM
    onAnchor() {}

    // called after onAnchor when the component is displayed in a browser context
    onDisplay() {}
}

It is recommended to use the onDisplay method to run user code that should be executed when the component has has finished rendering in the browser.

Children handling

Children can be added to components just like any other HTML element:

// add children with DOM APIs
const comp1 = new CustomComponent();
comp1.append(<div>content 1</div>);
comp1.append("text content");

// add children with JSX
const comp2 = 
    <CustomComponent>
        <div>Child 1</div>
        <div>Child 2</div>
    </CustomComponent>;

Component children are part of the component state and are restored when the component is recreated.

Component styling

See Styles and Themes.