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'use strict';

const emitter = () => {

const events = new Map();

const wrapped = new Map();

const ee = {

on: (name, f, timeout = 0) => {

const event = events.get(name);

if (event) event.push(f);

else events.set(name, [f]);

if (timeout) {

setTimeout(() => {

ee.remove(name, f);

}, timeout);

}

},

emit: (name, ...data) => {

const event = events.get(name);

event?.forEach((f) => f(...data));

},

once: (name, f) => {

const g = (...a) => {

ee.remove(name, g);

f(...a);

};

wrapped.set(f, g);

ee.on(name, g);

},

remove: (name, f) => {

const event = events.get(name);

if (!event) return;

let i = event.indexOf(f);

if (i !== -1) {

event.splice(i, 1);

return;

}

const g = wrapped.get(f);

if (g) {

i = event.indexOf(g);

if (i !== -1) event.splice(i, 1);

if (!event.length) events.delete(name);

}

},

clear: (name) => {

if (name) events.delete(name);

else events.clear();

},

count: (name) => {

const event = events.get(name);

return event?.length ?? 0;

},

listeners: (name) => {

const event = events.get(name);

return event.slice();

},

names: () => [...events.keys()],

};

return ee;

};

// Usage

const ee = emitter();

// on and emit

ee.on('e1', (data) => {

console.dir(data);

});

ee.emit('e1', { msg: 'e1 ok' });

// once

ee.once('e2', (data) => {

console.dir(data);

});

ee.emit('e2', { msg: 'e2 ok' });

ee.emit('e2', { msg: 'e2 not ok' });

// remove

const f3 = (data) => {

console.dir(data);

};

ee.on('e3', f3);

ee.remove('e3', f3);

ee.emit('e3', { msg: 'e3 not ok' });

// count

ee.on('e4', () => {});

ee.on('e4', () => {});

console.log('e4 count', ee.count('e4'));

// clear

ee.clear('e4');

ee.emit('e4', { msg: 'e4 not ok' });

ee.emit('e1', { msg: 'e1 ok' });

ee.clear();

ee.emit('e1', { msg: 'e1 not ok' });

// listeners and names

ee.on('e5', () => {});

ee.on('e5', () => {});

ee.on('e6', () => {});

ee.on('e7', () => {});

console.log('listeners', ee.listeners('e5'));

console.log('names', ee.names());