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JavaScript

'use strict';
const anyMap = new WeakMap();
const eventsMap = new WeakMap();
const producersMap = new WeakMap();
const anyProducer = Symbol('anyProducer');
const resolvedPromise = Promise.resolve();
const listenerAdded = Symbol('listenerAdded');
const listenerRemoved = Symbol('listenerRemoved');
function assertEventName(eventName) {
if (typeof eventName !== 'string' && typeof eventName !== 'symbol') {
throw new TypeError('eventName must be a string or a symbol');
}
}
function assertListener(listener) {
if (typeof listener !== 'function') {
throw new TypeError('listener must be a function');
}
}
function getListeners(instance, eventName) {
const events = eventsMap.get(instance);
if (!events.has(eventName)) {
events.set(eventName, new Set());
}
return events.get(eventName);
}
function getEventProducers(instance, eventName) {
const key = typeof eventName === 'string' || typeof eventName === 'symbol' ? eventName : anyProducer;
const producers = producersMap.get(instance);
if (!producers.has(key)) {
producers.set(key, new Set());
}
return producers.get(key);
}
function enqueueProducers(instance, eventName, eventData) {
const producers = producersMap.get(instance);
if (producers.has(eventName)) {
for (const producer of producers.get(eventName)) {
producer.enqueue(eventData);
}
}
if (producers.has(anyProducer)) {
const item = Promise.all([eventName, eventData]);
for (const producer of producers.get(anyProducer)) {
producer.enqueue(item);
}
}
}
function iterator(instance, eventNames) {
eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
let isFinished = false;
let flush = () => {};
let queue = [];
const producer = {
enqueue(item) {
queue.push(item);
flush();
},
finish() {
isFinished = true;
flush();
}
};
for (const eventName of eventNames) {
getEventProducers(instance, eventName).add(producer);
}
return {
async next() {
if (!queue) {
return {done: true};
}
if (queue.length === 0) {
if (isFinished) {
queue = undefined;
return this.next();
}
await new Promise(resolve => {
flush = resolve;
});
return this.next();
}
return {
done: false,
value: await queue.shift()
};
},
async return(value) {
queue = undefined;
for (const eventName of eventNames) {
getEventProducers(instance, eventName).delete(producer);
}
flush();
return arguments.length > 0 ?
{done: true, value: await value} :
{done: true};
},
[Symbol.asyncIterator]() {
return this;
}
};
}
function defaultMethodNamesOrAssert(methodNames) {
if (methodNames === undefined) {
return allEmitteryMethods;
}
if (!Array.isArray(methodNames)) {
throw new TypeError('`methodNames` must be an array of strings');
}
for (const methodName of methodNames) {
if (!allEmitteryMethods.includes(methodName)) {
if (typeof methodName !== 'string') {
throw new TypeError('`methodNames` element must be a string');
}
throw new Error(`${methodName} is not Emittery method`);
}
}
return methodNames;
}
const isListenerSymbol = symbol => symbol === listenerAdded || symbol === listenerRemoved;
class Emittery {
static mixin(emitteryPropertyName, methodNames) {
methodNames = defaultMethodNamesOrAssert(methodNames);
return target => {
if (typeof target !== 'function') {
throw new TypeError('`target` must be function');
}
for (const methodName of methodNames) {
if (target.prototype[methodName] !== undefined) {
throw new Error(`The property \`${methodName}\` already exists on \`target\``);
}
}
function getEmitteryProperty() {
Object.defineProperty(this, emitteryPropertyName, {
enumerable: false,
value: new Emittery()
});
return this[emitteryPropertyName];
}
Object.defineProperty(target.prototype, emitteryPropertyName, {
enumerable: false,
get: getEmitteryProperty
});
const emitteryMethodCaller = methodName => function (...args) {
return this[emitteryPropertyName][methodName](...args);
};
for (const methodName of methodNames) {
Object.defineProperty(target.prototype, methodName, {
enumerable: false,
value: emitteryMethodCaller(methodName)
});
}
return target;
};
}
constructor() {
anyMap.set(this, new Set());
eventsMap.set(this, new Map());
producersMap.set(this, new Map());
}
on(eventNames, listener) {
assertListener(listener);
eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
for (const eventName of eventNames) {
assertEventName(eventName);
getListeners(this, eventName).add(listener);
if (!isListenerSymbol(eventName)) {
this.emit(listenerAdded, {eventName, listener});
}
}
return this.off.bind(this, eventNames, listener);
}
off(eventNames, listener) {
assertListener(listener);
eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
for (const eventName of eventNames) {
assertEventName(eventName);
getListeners(this, eventName).delete(listener);
if (!isListenerSymbol(eventName)) {
this.emit(listenerRemoved, {eventName, listener});
}
}
}
once(eventNames) {
return new Promise(resolve => {
const off = this.on(eventNames, data => {
off();
resolve(data);
});
});
}
events(eventNames) {
eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
for (const eventName of eventNames) {
assertEventName(eventName);
}
return iterator(this, eventNames);
}
async emit(eventName, eventData) {
assertEventName(eventName);
enqueueProducers(this, eventName, eventData);
const listeners = getListeners(this, eventName);
const anyListeners = anyMap.get(this);
const staticListeners = [...listeners];
const staticAnyListeners = isListenerSymbol(eventName) ? [] : [...anyListeners];
await resolvedPromise;
await Promise.all([
...staticListeners.map(async listener => {
if (listeners.has(listener)) {
return listener(eventData);
}
}),
...staticAnyListeners.map(async listener => {
if (anyListeners.has(listener)) {
return listener(eventName, eventData);
}
})
]);
}
async emitSerial(eventName, eventData) {
assertEventName(eventName);
const listeners = getListeners(this, eventName);
const anyListeners = anyMap.get(this);
const staticListeners = [...listeners];
const staticAnyListeners = [...anyListeners];
await resolvedPromise;
/* eslint-disable no-await-in-loop */
for (const listener of staticListeners) {
if (listeners.has(listener)) {
await listener(eventData);
}
}
for (const listener of staticAnyListeners) {
if (anyListeners.has(listener)) {
await listener(eventName, eventData);
}
}
/* eslint-enable no-await-in-loop */
}
onAny(listener) {
assertListener(listener);
anyMap.get(this).add(listener);
this.emit(listenerAdded, {listener});
return this.offAny.bind(this, listener);
}
anyEvent() {
return iterator(this);
}
offAny(listener) {
assertListener(listener);
this.emit(listenerRemoved, {listener});
anyMap.get(this).delete(listener);
}
clearListeners(eventNames) {
eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
for (const eventName of eventNames) {
if (typeof eventName === 'string' || typeof eventName === 'symbol') {
getListeners(this, eventName).clear();
const producers = getEventProducers(this, eventName);
for (const producer of producers) {
producer.finish();
}
producers.clear();
} else {
anyMap.get(this).clear();
for (const listeners of eventsMap.get(this).values()) {
listeners.clear();
}
for (const producers of producersMap.get(this).values()) {
for (const producer of producers) {
producer.finish();
}
producers.clear();
}
}
}
}
listenerCount(eventNames) {
eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
let count = 0;
for (const eventName of eventNames) {
if (typeof eventName === 'string') {
count += anyMap.get(this).size + getListeners(this, eventName).size +
getEventProducers(this, eventName).size + getEventProducers(this).size;
continue;
}
if (typeof eventName !== 'undefined') {
assertEventName(eventName);
}
count += anyMap.get(this).size;
for (const value of eventsMap.get(this).values()) {
count += value.size;
}
for (const value of producersMap.get(this).values()) {
count += value.size;
}
}
return count;
}
bindMethods(target, methodNames) {
if (typeof target !== 'object' || target === null) {
throw new TypeError('`target` must be an object');
}
methodNames = defaultMethodNamesOrAssert(methodNames);
for (const methodName of methodNames) {
if (target[methodName] !== undefined) {
throw new Error(`The property \`${methodName}\` already exists on \`target\``);
}
Object.defineProperty(target, methodName, {
enumerable: false,
value: this[methodName].bind(this)
});
}
}
}
const allEmitteryMethods = Object.getOwnPropertyNames(Emittery.prototype).filter(v => v !== 'constructor');
// Subclass used to encourage TS users to type their events.
Emittery.Typed = class extends Emittery {};
Object.defineProperty(Emittery.Typed, 'Typed', {
enumerable: false,
value: undefined
});
Object.defineProperty(Emittery, 'listenerAdded', {
value: listenerAdded,
writable: false,
enumerable: true,
configurable: false
});
Object.defineProperty(Emittery, 'listenerRemoved', {
value: listenerRemoved,
writable: false,
enumerable: true,
configurable: false
});
module.exports = Emittery;