JavaScript: The Backbone of Modern Web Development

console.log('Start');
setTimeout(() => console.log('Timeout'), 0);
Promise.resolve().then(() => console.log('Promise'));
console.log('End');
// Output: Start, End, Promise, Timeout

const obj = { a: 1 };
const protoObj = { b: 2 };
Object.setPrototypeOf(obj, protoObj);
console.log(obj.b); // 2

const { Board, Led } = require('johnny-five');
const board = new Board();
board.on('ready', () => {
    const led = new Led(13);
    led.blink(500);
});

const tf = require('@tensorflow/tfjs');
const model = tf.sequential();
model.add(tf.layers.dense({ units: 1, inputShape: [1] }));
model.compile({ optimizer: 'sgd', loss: 'meanSquaredError' });
const xs = tf.tensor2d([1, 2, 3, 4], [4, 1]);
const ys = tf.tensor2d([1, 3, 5, 7], [4, 1]);
model.fit(xs, ys).then(() => {
    model.predict(tf.tensor2d([5], [1, 1])).print();
});

const { app, BrowserWindow } = require('electron');
let mainWindow;
app.on('ready', () => {
    mainWindow = new BrowserWindow({ width: 800, height: 600 });
    mainWindow.loadFile('index.html');
});

// we send in the function as an argument to be
// executed from inside the calling function
function performOperation(a, b, cb) {
    var c = a + b;
    cb(c);
}

performOperation(2, 3, function(result) {
    // prints out 5
    console.log("The result of the operation is " + result);
})

// either of the following ways can be used to create a new object
var instance = {};
// or
var instance = Object.create(Object.prototype);
// or
var instance = new Object();

// supported since ES3
// the dot notation
instance.key = "A key's value";

// the square brackets notation
instance["key"] = "A key's value";

// supported since ES5
// setting a single property using Object.defineProperty
Object.defineProperty(instance, "key", {
    value: "A key's value",
    writable: true,
    enumerable: true,
    configurable: true
});

// setting multiple properties using Object.defineProperties
Object.defineProperties(instance, {
    "firstKey": {
        value: "First key's value",
        writable: true
    },
    "secondKey": {
        value: "Second key's value",
        writable: false
    }
});

// we define a constructor for Person objects
function Person(name, age, isDeveloper) {
    this.name = name;
    this.age = age;
    this.isDeveloper = isDeveloper || false;

    this.writesCode = function() {
      console.log(this.isDeveloper? "This person does write code" : "This person does not write code");
    }
}

// creates a Person instance with properties name: Bob, age: 38, isDeveloper: true and a method writesCode
var person1 = new Person("Bob", 38, true);
// creates a Person instance with properties name: Alice, age: 32, isDeveloper: false and a method writesCode
var person2 = new Person("Alice", 32);

// prints out: This person does write code
person1.writesCode();
// prints out: this person does not write code
person2.writesCode();

// we define a constructor for Person objects
function Person(name, age, isDeveloper) {
    this.name = name;
    this.age = age;
    this.isDeveloper = isDeveloper || false;
}

// we extend the function's prototype
Person.prototype.writesCode = function() {
    console.log(this.isDeveloper? "This person does write code" : "This person does not write code");
}

// creates a Person instance with properties name: Bob, age: 38, isDeveloper: true and a method writesCode
var person1 = new Person("Bob", 38, true);
// creates a Person instance with properties name: Alice, age: 32, isDeveloper: false and a method writesCode
var person2 = new Person("Alice", 32);

// prints out: This person does write code
person1.writesCode();
// prints out: this person does not write code
person2.writesCode();