createComponent function #

The createComponent function defines a new component containing internal reactive state with the provided tag plus declarative object and registers it in the browser as a custom element.

Internally, the createComponent function uses the createCustomElement function and extends it with the withLocalState function.

Component names require a dash to be used in them; they cannot be single words - this is mandatory according to the custom element API.

Arguments #

When using the createComponent function, you must pass two arguments:

  1. tag name (for example my-component) - names require a dash to be used in them; they cannot be single words
  2. an object that defines the properties of the component

The following properties are used when creating components:

PropertyRequiredTypeDescription
rendereryesfunctionA function that renders what is returned from the render function
renderyesfunctionA function that must return a response that can be passed to the renderer function for creating HTML
rootstringSets the root definition for the component
propsobjectDescribes one or more property definitions - these are attributes and instance properties that can be set when using the component
computedobjectContains one or more getters (functions that act like properties) that are useful when rendering
statefunctionFunction that returns an object containing initial state. State is internal variables in the component
*functionFunctions that are useful in performing actions and logic
createdfunctionInvoked when the component is created and before it is connected to the DOM
mountedfunctionInvoked when the component is first connected to the DOM. This may trigger before the components contents have been fully rendered
updatedfunctionInvoked when the component is moved or reconnected to the DOM. This may trigger before the components contents have been fully rendered
removedfunctionInvoked each time the component is disconnected from the DOM

State #

The createComponent function provides reactive internal state using a Proxy.

Provide the state property of your config object to set initial state. Every time a value of your state is updated, your component will re-render.

You can access state with this.state in your component render function.

render () {
return html`<div>Hello, I'm ${this.state.name}</div>`
}

Initial state function #

The component's state option must be a function, so that each instance can maintain an independent copy of the returned state object.
This also allows you to use prop values as initial state.

If state is not a function, changing state in one instance would affect the state of all other instances.

{
props: {
count: {
type: Number,
default: 0
}
},
state () {
return {
count: this.props.count
}
}
}

Mutating state #

Mutating state can be done using direct assignment or the setState method.

Direct assignment #

Mutating state values can be done using direct assignment.

this.state.name = 'new name value'

setState method #

The setState method can be used to set one or more state values in a single transaction. This will only trigger a single render update. An optional callback can be provided which is invoked after rendering has occurred.

The setState function takes two arguments:

  1. State setter function (receives the current state as an argument)
  2. An optional callback which is invoked after rendering
this.setState(
(state) => {
return {
// return new state property values
}
},
() => {
// do something after rendering
}
)

Example component using setState method

// import the createComponent function
import { createComponent } from 'https://cdn.skypack.dev/ficusjs@3/component'

// import the renderer and html tagged template literal from the uhtml renderer
import { html, renderer } from 'https://cdn.skypack.dev/@ficusjs/renderers@3/uhtml'

createComponent('set-state-example', {
renderer,
state () {
return {
count: 0,
isEven: false,
color: 'secondary'
}
},
increment () {
this.setState(
(state) => {
const count = state.count + 1
const isEven = count % 2 === 0
return {
count,
isEven,
color: isEven ? 'success' : 'info'
}
},
() => console.log('Component did render!')
)
},
render () {
return html`<button type="button" @click=${this.increment} class="${this.state.color}">Count is&nbsp;<strong>${this.state.count}</strong></button>`
}
})