add node.js examples

_expressjs/hello-world.js

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+"use strict";
+
+const express = require("express");
+const app = express();
+const port = 8209;
+
+app.get("/", function (req, res) {
+    res.send("Hello World!");
+});
+
+app.listen(port, function () {
+    console.log(`Example app listening on port ${port}`);
+});

_nodejs/01a-hello-world/hello-world.js

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+"use strict";
+console.log("Hello World!");

_nodejs/01b-hello-world-server/hello-world-server.js

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+"use strict";
+
+const http = require("http");
+const hostname = "127.0.0.1";
+const port = 4003;
+
+const server = http.createServer((req, res) => {
+    res.statusCode = 200;
+    res.setHeader("Content-Type", "text/plain");
+    res.end("Hello World!");
+});
+
+server.listen(port, hostname, () => {
+    console.log(`Server running at http://${hostname}:${port}/`);
+});

_nodejs/02a-timers/timer.js

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+"use strict";
+
+let times = 0;
+let a = setInterval(()=>{
+    const max_times = 10;
+    if(++times > max_times)
+    {
+        clearInterval(a);
+    }
+    else
+    {
+        console.log(`Callback called ${times} times.`);
+    }
+}, 500);

_nodejs/03a-console/time.js

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+"use strict";
+
+const label = "10-times"
+let times = 0;
+console.time(label);
+let a = setInterval(()=>{
+    const max_times = 10;
+    if(++times > max_times)
+    {
+        clearInterval(a);
+        console.timeEnd(label);
+    }
+    else
+    {
+        console.log(`Callback called ${times} times.`);
+    }
+}, 500);

_nodejs/04a-modules/main-test.js

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+"use strict";
+console.log(`Am I the main program? ${require.main === module}`);
+console.log(`My name is ${require.main.filename}`);

_nodejs/04b-modules/module.js

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+"use strict";
+
+const mocha = require("mocha");
+
+console.log(module.filename);
+console.log(module.id);
+console.log(module.loaded);
+console.log("Module children:");
+module.children.forEach((child) => {
+    console.log(child.id);
+});

_nodejs/05a-os/system.js

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+"use strict";
+
+const os = require("os");
+
+let GIGABYTE = 9.31322575 * 1e-10;
+let type = os.type();
+let platform = os.platform();
+let release = os.release();
+let arch = os.arch();
+let hostname = os.hostname();
+let homedir = os.homedir();
+let memory = os.totalmem() * GIGABYTE;
+let fmemory = os.freemem() * GIGABYTE;
+let networkInterfaces = os.networkInterfaces();
+let cpus = os.cpus();
+
+console.log("Type: " + type);
+console.log("Platform: " + platform);
+console.log("Release: " + release);
+console.log("Architecture: " + arch);
+console.log("Hostname: " + hostname);
+console.log("Homedir: " + homedir);
+console.log("Memory: " + memory + " GB");
+console.log("Free memory: " + fmemory + " GB");
+console.log("Network: " + JSON.stringify(networkInterfaces, null, 4));
+console.log("CPUs: " + JSON.stringify(cpus, null, 4));

_nodejs/06a-events/my-emitter-driver.js

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+"use strict";
+
+const MyEmitter = require("./my-emitter");
+const myEmitter = new MyEmitter();
+
+myEmitter.on("event", function (s, i)
+{
+    if(i < 2)
+    {
+        console.log(this);
+    }
+    console.log(s);
+});
+myEmitter.once("one", function ()
+{
+    console.log("single event occurred!");
+});
+for(let i = 1; i < 3; i++)
+{
+    myEmitter.emit("event", `(${i}) an event occurred!`, i);
+    myEmitter.emit("one");
+}

_nodejs/06a-events/my-emitter.js

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+"use strict";
+
+const EventEmitter = require('events');
+
+module.exports = class MyEmitter extends EventEmitter {};

_nodejs/06b-events/my-emitter-driver.js

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+"use strict";
+
+const MyEmitter = require("./my-emitter");
+const myEmitter = new MyEmitter();
+
+myEmitter.on("error", (err) =>
+{
+    console.error(err.message);
+});
+
+myEmitter.emit("error", new Error("I am an error!"));

_nodejs/06b-events/my-emitter.js

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+"use strict";
+
+const EventEmitter = require('events');
+
+module.exports = class MyEmitter extends EventEmitter {};

_nodejs/06c-events/my-emitter-driver.js

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+"use strict";
+
+const MyEmitter = require("./my-emitter");
+const myEmitter = new MyEmitter();
+
+for(let i = 1; i < 3; i++)
+{
+    myEmitter.emit("event", `(${i}) an event occurred!`, i);
+    myEmitter.emit("one");
+}

_nodejs/06c-events/my-emitter.js

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+"use strict";
+
+const EventEmitter = require('events');
+
+module.exports = class MyEmitter extends EventEmitter
+{
+    constructor()
+    {
+        super();
+        this.on("event", function (s, i)
+        {
+            if(i < 2)
+            {
+                console.log(this);
+            }
+            console.log(s);
+        });
+        this.once("one", function ()
+        {
+            console.log("single event occurred!");
+        });
+    }
+};

_nodejs/07a-errors/error1.js

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+"use strict";
+try
+{
+    const m = 1;
+    const n = m + z;
+}
+catch (err) 
+{
+    console.error(err instanceof ReferenceError);
+    console.error(err.name);
+    console.error(err.message);
+    console.error(err.stack);
+}

_nodejs/07a-errors/error2.js

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+"use strict";
+const fs = require("fs");
+fs.readFile("a.xyz", (err, data) =>
+{
+    if (err) 
+    {
+        console.error(err.message);
+    }
+    else
+    {
+        console.log("File 'a.xyz' exists!");
+    }
+});

_nodejs/07a-errors/error3.js

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+"use strict";
+const net = require("net");
+const connection = net.connect("localhost");
+
+connection.on("error", (err) =>
+{
+    console.error(err.message);
+});

_nodejs/07b-errors/custom-error.js

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+"use strict";
+module.exports = class CustomError extends Error
+{
+    constructor(msg)
+    {
+        super();
+        this.name = this.constructor.name;
+        this.message = msg || CustomError.defaultMessage;
+    }
+
+    static get defaultMessage()
+    {
+        return "Customized Error";
+    }
+};

_nodejs/07b-errors/error1.js

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+"use strict";
+const CustomError = require("./custom-error");
+try
+{
+    throw new CustomError();
+}
+catch (err) 
+{
+    console.error(err instanceof CustomError);
+    console.error(err.name);
+    console.error(err.message);
+    console.error(err.stack);
+}

_nodejs/08a-process/process1.js

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+"use strict";
+
+start();
+console.log(`##### Process title: ${process.title}`);
+console.log(`##### Process version: ${process.version}`);
+console.log(`##### Process ID: ${process.pid}`);
+console.log(`##### Process arguments: ${process.argv}`);
+console.log(`##### Process execution path: ${process.execPath}`);
+console.log(`##### Process execution arguments: ${process.execArgv}`);
+console.log(`##### Process version: ${process.version}`);
+console.log(`##### Process architecture: ${process.arch}`);
+console.log(`##### Process platform: ${process.platform}`);
+console.log(`##### Process current directory: ${process.cwd()}`);
+console.log("##### Process versions:\n" + JSON.stringify(process.versions, null, 4));
+console.log("##### Process configuration:\n" + JSON.stringify(process.config, null, 4));
+
+process.on("exit", (code) =>
+{
+    console.log("##### Process memory usage: " +  JSON.stringify(process.memoryUsage(), null, 0));
+    console.log(`##### Process uptime: ${process.uptime()}`);
+    console.log(`##### Finishing the process with code ${code} #####`);
+});
+
+process.on("uncaughtException", (err) =>
+{
+    console.log(`##### Exception caught: ${err.message}`);
+});
+
+function start()
+{
+    console.log("##### Starting the process #####");
+}

_nodejs/08a-process/process2.js

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+"use strict";
+
+console.log("##### Process environment variables before change: " +
+    JSON.stringify(process.env, null, 4));
+process.env["HISTSIZE"] = 10;
+console.log("##### Process environment variables after change: " +
+    JSON.stringify(process.env, null, 4));

_nodejs/08a-process/process3.js

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+"use strict";
+
+process.on("exit", (code) =>
+{
+    console.log("##### Process memory usage: " +  JSON.stringify(process.memoryUsage(), null, 0));
+    console.log(`##### Process uptime: ${process.uptime()}`);
+    console.log(`##### Finishing the process with code ${code} #####`);
+});
+
+process.on("uncaughtException", (err) =>
+{
+    console.log(`##### Exception caught: ${err.message}`);
+    process.exit(1);
+});
+
+start();

_nodejs/09a-buffer/buffer1.js

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+"use strict";
+
+const buf = Buffer.from("¡Hola! ¿Cómo estáis?", "utf8");
+let i = 0;
+for (let b of buf)
+{
+    console.log(`element: ${i++} - decimal: ${b} - hex: ${b.toString(16)}`);
+}

_nodejs/09a-buffer/buffer2.js

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+"use strict";
+
+const buf = Buffer.alloc(1, "¡", "utf8");
+let i = 0;
+for (let b of buf)
+{
+    console.log(`element: ${i++} - decimal: ${b} - hex: ${b.toString(16)}`);
+}

_nodejs/09a-buffer/buffer3.js

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+"use strict";
+
+const str = "¡Hola! ¿Cómo estáis?";
+const buf = Buffer.from(str, "utf8");
+console.log(`buffer byte length: ${buf.byteLength} - string length: ${str.length}`);

_nodejs/10a-child_process/cp1.js

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+"use strict";
+const cp = require("child_process");
+if (process.platform === "win32")
+{
+    console.log("Unsupported platform!");
+    process.exit(0);
+}
+const ls = cp.spawn("ls", ["-lh", "/tmp"]);
+
+ls.stdout.on("data", (data) => {
+    console.log(`stdout: ${data}`);
+});
+
+ls.stderr.on("data", (data) => {
+    console.log(`stderr: ${data}`);
+});
+
+ls.on("close", (code) => {
+    console.log(`child process exited with code ${code}`);
+});

_nodejs/10a-child_process/cp2.js

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+"use strict";
+const cp = require("child_process");
+let ls;
+if (process.platform === "win32")
+{
+    ls = cp.spawn("cmd.exe", ["/c", "dir", process.env["TEMP"]]);
+}
+else
+{
+    ls = cp.spawn("ls", ["-lh", "/tmp"]);
+}
+
+ls.stdout.on("data", (data) => {
+    console.log(`stdout: ${data}`);
+});
+
+ls.stderr.on("data", (data) => {
+    console.log(`stderr: ${data}`);
+});
+
+ls.on("close", (code) => {
+    console.log(`child process exited with code ${code}`);
+});