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Improve some event-*.js examples for better usage #20

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ab72e4e
Improve example usage
Vladyulik Jun 19, 2025
f1fb78e
Improve example usage
Vladyulik Jun 19, 2025
52078a5
Improve example usage
Vladyulik Jun 19, 2025
75eaf1a
Improve example usage
Vladyulik Jun 19, 2025
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40 changes: 23 additions & 17 deletions JavaScript/event-aggregation.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,36 +3,42 @@
const { EventEmitter } = require('node:events');

class Point {
static #bus = new EventEmitter();

#x;
#y;
#id;

constructor({ x, y }, emitter) {
constructor({ x, y }) {
this.#x = x;
this.#y = y;
this.#id = Symbol('point');

emitter.on('move', ({ x, y }) => {
Point.#bus.on(`move:${this.#id.description}`, ({ x, y }) => {
this.#x += x;
this.#y += y;
return this;
});

emitter.on('clone', (callback) => {
const point = new Point({ x: this.#x, y: this.#y }, emitter);
callback(point);
});
Point.#bus.on(`clone:${this.#id.description}`, () => new Point({ x: this.#x, y: this.#y }));

emitter.on('toString', (callback) => {
callback(`(${this.#x}, ${this.#y})`);
});
Point.#bus.on(`toString:${this.#id.description}`, () => `(${this.#x}, ${this.#y})`);
}

emit(type, payload) {
const listener = Point.#bus.listeners(`${type}:${this.#id.description}`)[0];
if (!listener) throw new Error(`Unknown event: ${type}`);
return listener(payload);
}
}

// Usage

const emitter = new EventEmitter();
const p1 = new Point({ x: 10, y: 20 }, emitter);
emitter.emit('toString', console.log);
emitter.emit('clone', (c0) => {
emitter.emit('toString', console.log);
emitter.emit('move', { x: -5, y: 10 });
emitter.emit('toString', console.log);
});
const p1 = new Point({ x: 10, y: 20 });
console.log(p1.emit('toString'));

const c1 = p1.emit('clone');
console.log(c1.emit('toString'));

c1.emit('move', { x: -5, y: 10 });
console.log(c1.emit('toString'));
33 changes: 18 additions & 15 deletions JavaScript/event-compose.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5,34 +5,37 @@ const { EventEmitter } = require('node:events');
class Point {
#x;
#y;
#emitter;

constructor({ x, y }) {
this.#x = x;
this.#y = y;
this.emitter = new EventEmitter();
this.#emitter = new EventEmitter();

this.emitter.on('move', ({ x, y }) => {
this.#emitter.on('move', ({ x, y }) => {
this.#x += x;
this.#y += y;
});

this.emitter.on('clone', (callback) => {
const point = new Point({ x: this.#x, y: this.#y });
callback(point);
});
this.#emitter.on('clone', () => new Point({ x: this.#x, y: this.#y }));

this.emitter.on('toString', (callback) => {
callback(`(${this.#x}, ${this.#y})`);
});
this.#emitter.on('toString', () => `(${this.#x}, ${this.#y})`);
}

emit(eventName, arg) {
const listener = this.#emitter.listeners(eventName)[0];
if (!listener) throw new Error(`Unknown event: ${eventName}`);
return listener(arg);
}
}

// Usage

const p1 = new Point({ x: 10, y: 20 });
p1.emitter.emit('toString', console.log);
p1.emitter.emit('clone', (c1) => {
c1.emitter.emit('toString', console.log);
c1.emitter.emit('move', { x: -5, y: 10 });
c1.emitter.emit('toString', console.log);
});
console.log(p1.emit('toString'));

const c1 = p1.emit('clone');
console.log(c1.emit('toString'));

c1.emit('move', { x: -5, y: 10 });
console.log(c1.emit('toString'));
36 changes: 20 additions & 16 deletions JavaScript/event-target.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,46 +4,50 @@ class PointEvent extends Event {
constructor(type, detail = {}) {
super(type);
this.detail = detail;
this.result = undefined;
}
}

class Point {
#x;
#y;
#target;

constructor({ x, y }) {
this.#x = x;
this.#y = y;
this.target = new EventTarget();
this.#target = new EventTarget();

this.target.addEventListener('move', (event) => {
const { x: dx, y: dy } = event.detail;
this.#target.addEventListener('move', (e) => {
const { x: dx, y: dy } = e.detail;
this.#x += dx;
this.#y += dy;
e.result = this;
});

this.target.addEventListener('clone', (event) => {
event.detail.callback(new Point({ x: this.#x, y: this.#y }));
this.#target.addEventListener('clone', (e) => {
e.result = new Point({ x: this.#x, y: this.#y });
});

this.target.addEventListener('toString', (event) => {
event.detail.callback(`(${this.#x}, ${this.#y})`);
this.#target.addEventListener('toString', (e) => {
e.result = `(${this.#x}, ${this.#y})`;
});
}

emit(type, detail = {}) {
this.target.dispatchEvent(new PointEvent(type, detail));
const event = new PointEvent(type, detail);
this.#target.dispatchEvent(event);
return event.result;
}
}

// Usage

const p1 = new Point({ x: 10, y: 20 });
p1.emit('toString', { callback: console.log });
p1.emit('clone', {
callback: (c1) => {
c1.emit('toString', { callback: console.log });
c1.emit('move', { x: -5, y: 10 });
c1.emit('toString', { callback: console.log });
},
});
console.log(p1.emit('toString'));

const c1 = p1.emit('clone');
console.log(c1.emit('toString'));

c1.emit('move', { x: -5, y: 10 });
console.log(c1.emit('toString'));