map() Create

map() Create demo built with Expressive MVC - the complete source below runs as an editable sandbox when JavaScript is enabled.

import './App.css';

import { Component, get, map } from '@expressive/react';

const PEOPLE = ['alice', 'bob', 'carol', 'dave'];
const STATUS = ['online', 'away', 'busy'];

// The room owns the people, keyed by id, and spawns them with a second
// argument: set(id, name) forwards to the factory. The detail reads
// people.get(selected), which subscribes to that one key - so it
// re-renders when the selected person changes, not when the others do.
export default class Room extends Component {
  people = map((id: string) => new Person({ id, name: capitalize(id) }));
  selected = '';

  protected new() {
    for (const name of PEOPLE) this.people.set(name);
    [this.selected] = PEOPLE;
  }

  render() {
    const { people, selected } = this;
    const active = people.get(selected);

    return (
      <div className="container room">
        <h1>Presence</h1>
        <p>
          Click a name to select; click a status dot to cycle it. The detail
          reads <code>people.get(selected)</code>, so it tracks only that key.
        </p>

        <div className="layout">
          <ul className="people">{people}</ul>

          <aside className="detail">
            {active ? (
              <>
                <span className={`dot lg ${active.status}`} />
                <h2>{active.name}</h2>
                <p className="status">{active.status}</p>
                <button onClick={() => active.cycle()}>Cycle status</button>
              </>
            ) : (
              <p className="empty">Select someone</p>
            )}
          </aside>
        </div>
      </div>
    );
  }
}

// A person is a spawned, owned member keyed by id. It reads get(Room) to
// reflect and change the selection.
class Person extends Component {
  room = get(Room);
  id = '';
  name = '';
  status = 'online';

  cycle() {
    this.status = STATUS[(STATUS.indexOf(this.status) + 1) % STATUS.length];
  }

  render() {
    const { id, name, status, room } = this;

    return (
      <li
        className={room.selected === id ? 'person selected' : 'person'}
        onClick={() => (room.selected = id)}>
        <span className={`dot ${status}`} onClick={(e) => { e.stopPropagation(); this.cycle(); }} />
        <span className="name">{name}</span>
      </li>
    );
  }
}

function capitalize(s: string) {
  return s.charAt(0).toUpperCase() + s.slice(1);
}

.room {
  max-width: 32rem;
}

.room .layout {
  display: grid;
  grid-template-columns: 1fr 12rem;
  gap: var(--s4);
  width: 100%;
  align-items: start;
}

ul.people {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--s1);
}

.person {
  display: flex;
  align-items: center;
  gap: var(--s3);
  padding: var(--s2) var(--s3);
  border: 1px solid transparent;
  border-radius: var(--r);
  cursor: pointer;
  text-align: left;
}

.person:hover {
  background: var(--surface);
}

.person.selected {
  background: var(--accent-soft);
  border-color: var(--accent);
}

.person .name {
  font-size: var(--t-base);
  color: var(--fg);
}

.dot {
  width: 0.6rem;
  height: 0.6rem;
  border-radius: 50%;
  flex-shrink: 0;
  cursor: pointer;
  background: var(--muted);
}

.dot.lg {
  width: 1rem;
  height: 1rem;
}

.dot.online {
  background: #10b981;
}

.dot.away {
  background: #f59e0b;
}

.dot.busy {
  background: #ef4444;
}

.detail {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--s2);
  padding: var(--s4);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  text-align: center;
}

.detail h2 {
  margin: 0;
  font-size: var(--t-lg);
}

.detail .status {
  margin: 0;
  font-size: var(--t-sm);
  color: var(--muted);
  text-transform: capitalize;
}

.detail button {
  margin-top: var(--s2);
  padding: var(--s2) var(--s3);
  font: inherit;
  font-size: var(--t-sm);
  color: var(--fg);
  background: var(--bg);
  border: 1px solid var(--border-2);
  border-radius: var(--r-sm);
  cursor: pointer;
}

.detail button:hover {
  border-color: var(--accent);
}

.detail .empty {
  color: var(--muted);
  font-size: var(--t-sm);
}