joist-handlers-1.ts

import { component, State, handle, JoistElement, get } from '@joist/component';
import { template, html } from '@joist/component/lit-html';

@component({
  tagName: 'my-counter',
  state: 0,
  render: template(({ state, run }) => {
    return html`
      <button @click=${run('decrement')}>-</button>
      <span>${state}</span>
      <button @click=${run('increment')}>+</button>
    `
  })
})
class AppElement extends JoistElement {
  @get(State)
  private state!: State<number>;

  @handle('increment') 
  increment() {
    this.state.setValue(this.state.value + 1);
  }

  @handle('decrement') 
  decrement() {
    this.state.setValue(this.state.value - 1);
  }
}