The rest of the GoF catalogue at a glance

// emoji-art.tsexport class EmojiArt {  constructor(readonly name: string, readonly pixels: Uint8Array) {}  draw(x: number, y: number): string { return `${this.name} at ${x},${y}`; }}const loaded = new Map<string, EmojiArt>();export function emojiArt(name: string): EmojiArt {  let art = loaded.get(name);  if (!art) { art = new EmojiArt(name, new Uint8Array(64 * 64)); loaded.set(name, art); }  return art;} // reaction.tsimport { EmojiArt, emojiArt } from './emoji-art';export class Reaction {  readonly art: EmojiArt;  constructor(name: string, readonly x: number, readonly y: number) { this.art = emojiArt(name); }  render(): string { return this.art.draw(this.x, this.y); }}

// composer.tsexport interface Saved { readonly at: number; }class ComposerState implements Saved {  constructor(readonly at: number, readonly text: string, readonly cursor: number) {}}export class Composer {  private text = '';  private cursor = 0;  type(s: string): void { this.text += s; this.cursor = this.text.length; }  save(at: number): Saved { return new ComposerState(at, this.text, this.cursor); }  restore(s: Saved): void { const st = s as ComposerState; this.text = st.text; this.cursor = st.cursor; }} // draft-history.tsimport { Composer, Saved } from './composer';export class DraftHistory {  private stack: Saved[] = [];  constructor(private composer: Composer) {}  beforeEdit(at: number): void { this.stack.push(this.composer.save(at)); }  back(): void { const s = this.stack.pop(); if (s) this.composer.restore(s); }}

// templates.tsexport interface Template { title: string; clone(): Template; }export class Poll implements Template {  constructor(public title: string, public choices: string[], public closesInHours: number) {}  clone(): Poll { return new Poll(this.title, [...this.choices], this.closesInHours); }}export class IncidentAlert implements Template {  constructor(public title: string, public severity: 'sev1' | 'sev2', public pager: boolean) {}  clone(): IncidentAlert { return new IncidentAlert(this.title, this.severity, this.pager); }}export const templates = new Map<string, Template>([  ['lunch-poll', new Poll('Lunch?', ['pizza', 'sushi'], 2)],  ['db-down', new IncidentAlert('Database down', 'sev1', true)],]); // post.tsimport { templates, Template } from './templates';export function fromTemplate(name: string, title: string): Template {  const found = templates.get(name);  if (!found) throw new Error(`no template ${name}`);  const message = found.clone();  message.title = title;  return message;}

// channels.tsexport interface Channel { send(to: string, text: string): string; }export class PushChannel implements Channel {  send(to: string, text: string): string { return `push ${to}: ${text}`; }}export class EmailChannel implements Channel {  send(to: string, text: string): string { return `email ${to}: ${text}`; }} // notices.tsimport { Channel } from './channels';export abstract class Notice {  constructor(protected channel: Channel) {}  abstract deliver(to: string, about: string): string[];}export class MentionNotice extends Notice {  deliver(to: string, about: string): string[] { return [this.channel.send(to, `You were mentioned in ${about}`)]; }}export class DigestNotice extends Notice {  deliver(to: string, about: string): string[] { return about.split(',').map((t) => this.channel.send(to, `New in ${t}`)); }}

// walk.mjs (given)export function walk(node, visitor) {  visitor[node.type]?.(node);  for (const child of node.children ?? []) walk(child, visitor);} // notify-list.mjsexport function notifyList(authorId) {  // your code}

// party-parts.tsexport class Player {  position = 0;  constructor(private onSeek: (to: number) => void) {}  seekTo(to: number): void { this.position = to; this.onSeek(to); }  pause(): void {}}export class CommentsPanel {  lines: string[] = [];  post(line: string): void { this.lines.push(line); }}export class ReactionsBar {  mutedFor = 0;  constructor(private onBurst: () => void) {}  burst(): void { this.onBurst(); }  mute(seconds: number): void { this.mutedFor = seconds; }} // watch-party.tsimport { Player, CommentsPanel, ReactionsBar } from './party-parts';export class WatchParty {  comments = new CommentsPanel();  player = new Player((to) => { this.comments.post(`Jumped to ${to}s`); this.reactions.mute(3); });  reactions = new ReactionsBar(() => { this.player.pause(); this.comments.post('Paused for the reactions'); });}

// places.tsexport interface PlaceOp<R> { seat(s: Seat): R; box(b: Box): R; standing(a: Standing): R; }export interface Place { run<R>(op: PlaceOp<R>): R; }export class Seat implements Place {  constructor(readonly row: string, readonly n: number, readonly stepFree: boolean) {}  run<R>(op: PlaceOp<R>): R { return op.seat(this); }}export class Box implements Place {  constructor(readonly name: string, readonly chairs: number) {}  run<R>(op: PlaceOp<R>): R { return op.box(this); }}export class Standing implements Place {  constructor(readonly zone: string, readonly capacity: number) {}  run<R>(op: PlaceOp<R>): R { return op.standing(this); }} // pricing.tsimport { PlaceOp } from './places';export const pricing: PlaceOp<number> = {  seat: (s) => (s.row < 'F' ? 60 : 45),  box: (b) => 90 * b.chairs,  standing: () => 30,}; // takings.tsimport { Place } from './places';import { pricing } from './pricing';export const takings = (map: Place[]): number => map.reduce((sum, p) => sum + p.run(pricing), 0);