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zhaomengru2015/application-wide-singleton.mjs

Last active February 12, 2020 02:19
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nodeJs event emitter
Raw
application-wide-singleton.mjs
import { EventEmitter } from "events";
import express from 'express';
const eventEmitter = new EventEmitter();
const app = express();
app.set('eventEmitter', eventEmitter);
// access it from any module of the application
console.log(app.get('eventEmitter'));
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event-name.mjs
import { EventEmitter } from "events";
const eventEmitter = new EventEmitter();
eventEmitter.on("myEvent", data => console.log(data, "- ON"));
eventEmitter.on("myEvent2", data => console.log(data, "- ON"));
eventEmitter.once("myEvent3", data => console.log(data, "- ONCE"));
console.log(eventEmitter.eventNames());
eventEmitter.emit("myEvent3", 'EVENT');
console.log(eventEmitter.eventNames());
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once.mjs
import { EventEmitter } from "events";
const eventEmitter = new EventEmitter();
eventEmitter.on("myEvent", data => {
console.log(data, "- ON");
});
eventEmitter.once("myEvent", data => {
console.log(data, "- ONCE");
});
eventEmitter.emit("myEvent", "Emitted Statement");
eventEmitter.emit("myEvent", "Emitted Statement");
eventEmitter.emit("myEvent", "Emitted Statement");
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order.mjs
import { EventEmitter } from 'events';
const eventEmitter = new EventEmitter();
eventEmitter.on('myEvent', (data) => {
console.log(data, '- FIRST');
});
console.log('Statement A');
eventEmitter.on("myEvent", data => {
console.log(data, '- SECOND');
});
eventEmitter.emit('myEvent', 'Emitted Statement');
console.log("Statement B");
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process.mjs
process.on("exit", () => console.log("Exit"));
process.on('uncaughtException', () => {
console.log('Exception');
process.exit();
});
throw new Error('Test Error');
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read-file.mjs
import { createReadStream } from "fs";
let chunkIndex = 0;
const readStream = createReadStream("./data.txt");
readStream.on("open", () => {
console.log("Started Reading...");
});
readStream.on("end", () => {
console.log("Completed Reading...");
});
readStream.on("data", chunk => {
console.log("Chunk: " + ++chunkIndex);
console.log("-----------------------------------------");
console.log(chunk);
console.log("\n");
});
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remove-all-licenser.mjs
import { EventEmitter } from "events";
const eventEmitter = new EventEmitter();
function func1() {
console.log("EVENT TRIGGERED");
}
eventEmitter.on("myEvent", func1);
eventEmitter.on("myEvent2",func1);
eventEmitter.removeAllListeners();
console.log(eventEmitter.eventNames());
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remove-listener.mjs
import { EventEmitter } from "events";
const eventEmitter = new EventEmitter();
function func1() {
console.log("EVENT TRIGGERED");
}
eventEmitter.on("myEvent", func1);
eventEmitter.on("myEvent2", func1);
console.log(eventEmitter.eventNames());
eventEmitter.removeListener("myEvent", func1);
console.log(eventEmitter.eventNames());
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singleton.mjs
import { EventEmitter } from 'events';
const eventEmitter1 = new EventEmitter();
eventEmitter1.on('myEvent', () => {
console.log('Listener');
});
const eventEmitter2 = new EventEmitter();
eventEmitter2.emit('myEvent');
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subscribe-after-publish.mjs
import { EventEmitter } from 'events';
const eventEmitter = new EventEmitter();
eventEmitter.on('myEvent', () => {
console.log('Listener 1');
});
eventEmitter.emit('myEvent');
eventEmitter.on("myEvent", () => {
console.log("Listener 2");
});
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subscribe-before-publish.mjs
import { EventEmitter } from 'events';
const eventEmitter = new EventEmitter();
// listen to the event
eventEmitter.on('myEvent', () => {
console.log('Data Received');
});
// publish an event
eventEmitter.emit('myEvent');
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sync.mjs
import { EventEmitter } from 'events';
const eventEmitter = new EventEmitter();
eventEmitter.on('myEvent', (data) => {
console.log(data);
});
console.log('Statement A');
eventEmitter.emit('myEvent', 'Statement B');
console.log("Statement C");
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