valerymelou

function smile(isHappy) {
  if (isHappy) {
    var smiling = 'I am happy!';
  } else {
    var sad = 'I am sad!';
    console.log(smiling);
  }
}

smile(false);  // undefined

valerymelou

function smile(isHappy) {
  var smiling;
  var sad;
  if (isHappy) {
    smiling = 'I am happy!';
  } else {
    sad = 'I am sad!';
    console.log(smiling);
  }
}

valerymelou

function smile(isHappy) {
  if (isHappy) {
    const smiling = 'I am happy!';
  } else {
    const sad = 'I am sad!';
    console.log(smiling);
  }
}

smile(false);  // ReferenceError: smiling is not defined

valerymelou

var name = 'Valery Melou';
var message = 'Hello! My name is ' + name + '.';

console.log(message);  // Hello! My name is Valery Melou.

valerymelou

const name = 'John Doe';
const message = `Hello! My name is ${name}.`;

console.log(message);  // Hello! My name is John Doe.

valerymelou

let a = 10;
let b = 20;
let result = `The sum of ${a} and ${b} is ${a + b}.`

console.log(result);  // The sum of 10 and 20 is 30.

valerymelou

var coordinates = [10, 30, 5];
var x = coordinates[0];
var y = coordinates[1];
var z = coordinates[2];

console.log(x, y, z);  // 10 30 5

valerymelou

const coordinates = [10, 30, 5];
const [x, y, z] = coordinates;

console.log(x, y, z);  // 10 30 5

valerymelou

var person = {
  firstName: "John",
  lastName: "Doe",
  age: 15
};

var firstName = person.firstName;
var lastName = person.lastName;
var age = person.age;

valerymelou

let person = {
  firstName: "John",
  lastName: "Doe",
  age: 15
};

let {firstName, lastName, age} = person;

console.log(firstName, lastName, age);  // John Doe 15