# Codecademy: JavaScript

1. Introduction

"text";
"text".length;
3 + 4;
4 / 2;
14 % 3;
//comment
confirm("I feel awesome");
prompt("What is your name?");
["I'm coding like a champ!".length] > 10
console.log("Hello");
console.log(15 > 4);
console.log("Xiao Hui".length < 122);
console.log("Goody Donaldson".length != 8);
console.log(8*2 === 16);
console.log(true !== true);
if ( 1 > 2 ) {
 alert("I am right");
} else {
 console.log("I am wrong");
}
"wonderful day".substring(3,7);
var myName = "Leng";
var myAge = 30;
var isOdd = true;
myName.length;
var age = prompt("What's your age?");

2. Functions

var divideByThree = function (number) {
 var val = number / 3;
 console.log("Result = " + val);
};
divideByThree(6);

var timesTwo = function(number) {
 return number * 2;
};
var newNumber = timesTwo(2);
console.log(newNumber);

var perimeterBox  = function(length, width) {
 return length*2 + width*2;
};
perimeterBox(2,2);

var multiplied = 5; // Global
var timesTwo = function(number) {
 var multiplied = number * 2; // Local
};
timesTwo(4);
console.log(multiplied);

3. 'For' Loops

for (var counter = 1; counter < 11; counter++) {
 console.log(counter);
}

for (var i = 5; i <= 50; i+=5) {
 console.log(i);
}

for (var i = 10; i >= 0; i--) {
 console.log(i);
}

for (var i = 100; i >= 1; i-=5) {
 console.log(i);
}

var junk = ["Mao","Gandhi",1,2];
console.log(junk);
console.log(junk[0]);
console.log(junk.length);

4. 'While' Loops

var understand = true;
while( understand ){
 console.log("I'm learning while loops!");
 understand = false;
}

loopCondition = false;
do {
 console.log("I'm gonna stop looping 'cause my condition is " + String(loopCondition) + "!");
} while (loopCondition);

5. More on Control Flow

var lunch = prompt("What do you want for lunch?","Type your lunch choice here");
switch(lunch){
 case 'sandwich':
  console.log("Sure thing! One sandwich, coming up.");
  break;
 case 'soup':
  console.log("Got it! Tomato's my favorite.");
  break;
 case 'salad':
  console.log("Sounds good! How about a caesar salad?");
  break;
 case 'pie':
  console.log("Pie's not a meal!");
  break;
 default:
  console.log("Huh! I'm not sure what " + lunch + " is. How does a sandwich sound?");
}

true && true // => true
false || false // => false
!true // => false
!false // => true

6. Data Structures

var newArray = [[11,12,13], [21,22,23], [31,32,33]];
var jagged = [[11,12,13], [21], [31,32]];
var phonebookEntry = {};
phonebookEntry.name = 'Oxnard Montalvo';
phonebookEntry.number = '(555) 555-5555';
phonebookEntry.phone = function() {
 console.log('Calling ' + this.name + ' at ' + this.number + '...');
};
phonebookEntry.phone();

var myObj = new Object();
myObj["name"] = "Charlie";
myObj.name = "Charlie";

7. Objects I

var bob = {};
var bob = {
 name: "Bob Smith",
 age: 30
};
var name = bob.name;
var age = bob.age;

var dog = {
 species: "greyhound",
 weight: 60,
 age: 4
};
var species = dog["species"];
var weight = dog["weight"];
var age = dog["age"];

var bob = new Object();
bob.name = "Bob Smith";
bob.age = 30;
bob.setAge = function (newAge){
 this.age = newAge;
};
bob.setAge(40);

function Person(name,age) {
 this.name = name;
 this.age = age;
}
var bob = new Person("Bob Smith", 30);

var family = new Array();
family[0] = new Person("alice", 40);
family[1] = new Person("bob", 42);

var ageDifference = function(person1, person2) {
  return person1.age - person2.age;
}
var alice = new Person("Alice", 30);
var billy = new Person("Billy", 25);
var diff = ageDifference(alice,billy);

8. Objects II

var myObj = { job: "I'm an object!" };
console.log( typeof myObj ); // => object
console.log( myObj.hasOwnProperty('job') ); // => true

var nyc = {
 fullName: "New York City",
 mayor: "Michael Bloomberg",
 population: 8000000,
 boroughs: 5
};
for (var property in nyc){
 console.log(property);
}
for (var i in nyc){
 console.log(nyc[i]);
}

function Dog (breed) {
 this.breed = breed;
};
var buddy = new Dog("golden Retriever");
Dog.prototype.bark = function() {
 console.log("Woof");
};

function Animal(name, numLegs) {
 this.name = name;
 this.numLegs = numLegs;
}
Animal.prototype.sayName = function() {
 console.log("Hi my name is " + this.name);
};
function Penguin(name){
 this.name = name;
 this.numLegs = 2;
}
Penguin.prototype = new Animal();

function Person(first,last,age) {
 this.firstname = first;
 this.lastname = last;
 this.age = age;
 var bankBalance = 7500; // Private var
 this.getBalance = function() {
  return bankBalance;
 };
 var returnBalance = function() { // Private function
  return bankBalance;
 };     
 this.askTeller = function() {
   return returnBalance;
 }
}