Variables

var name = 'William';
var age = 23;

var name = 'Wiliam', age = 23, human = true;

var name = 'William',
    age = 23,
    human = true;

name = 'Marcelo';
human = false;
age = 'Veintitrés';

var salary = 200,
    expenses = 100;

var total = (salary - expenses);

var myFriend;
var my_friend;
var MyFriend;

// Invalid names
var 5riend;
var my-friend;

// Valid names
var π = Math.PI;
var ಠ_ಠ = eval;
    

Functions

function calcMoney(salary, expenses) {
  return salary - expenses;
}

calcMoney(500, 100);

var sum = function(a, b) {
    return a + b;
};

sum(2, 1);

sum = function(a, b, c, d) {
    return a + b + c + d;
}

sum(2, 1);
sum(2, 1, 0, 0);

function helloWorld() {
    var message = 'Hello world';
    return message;
}

Scope

var things = function() {
  var foo = 'bar';
};

things();
foo;

var greeting = 'hi';
var greets = function() {
  var greeting = 'Hello';
};

greeting;
greets();
greeting;

var greeting = 'hi';
var greets = function() {
  greeting = 'Hello';
};

greeting;
greets();
greeting;

Objects

var person = {
    firstName: 'William',
    lastName: 'Rhodes',
    age: 23,
    teacher: true,
    religion: undefined,
    car: null
};

person.name;
person.car = 'KIA';

person.children = {
    childOne: {
        name: 'Matthew',
        isACat: true
    },
    childTwo: {
        name: 'Leeloo'
    }
};

person.children.childOne.name;
person.children.childTwo.isACat;

var person = {
    walk: function() {
        console.log('Walking');
    }
};

var anotherPerson = person;

anotherPerson.walk;
anotherPerson.walk();

anotherPerson.getAge = function() {
    return 32;
};

var anotherPersonAge = anotherPerson.getAge();

var newAge = anotherPersonAge

newAge = newAge + 20 ;

newAge;
anotherPersonAge;

anotherPerson.age = 66;
person.age;

Arrays

var list = [ 'eggs', 'thing', 'carrots', 'some' ];

var numbers = [1, 3, 5];

list[0];
numbers[2];

numbers[5] = 'infinite';
numbers[4];

list.length;
list.join(', ');
list.push('strawberries')

var ALotOfPeople = [
  { name: 'Marcelo' }, 
  { name: 'Nancy' }
];

var person = ALotOfPeople[1];
ALotOfPeople[1];
ALotOfPeople[1].name;

person['name'];

person['nombre'] = 'Alan Britto';
ALotOfPeople[1].name;

The mean of "this"

var Utils = {
    door: 0,
    openDoor: function() {
        var that = this;
        this.door = 1;

        function openAgain() {
          this.door += 1;
          that.door += 1; 
        }

        openAgain();
    }
};

var App = {
    init: function() {
        this.cacheElements();
        this.bindEvents();
        Utils.openDoor();
    },
    cacheElements: function() {
        // TODO
    },
    bindEvents: function() {
        // TODO
    }
};

App.init();

Error handling

try {
  throw "Ooops!!! something happened";
} catch (err) {
  console.log(err);
}

try {
  throw new Error("Shot me down!");
} catch(err) {
  console.log(err.message);
  console.log(err.stack);
}

Iterations

var arr = [];
arr[1] = 'ohaiou';
arr[2] = 'morning';
 
for (var prop in arr) {
  console.log(prop, arr[prop]);
}

var person = {
    name : 'Tom',
    age: 23
};

person.name;
person['name'];

for ( var prop in person ) {
    console.log(prop);
}

Conditionals

var foo = 'hi';

if ( !parseFloat(foo) ) {
  console.log(!parseFloat(foo));
}

foo = '0';

if ( !parseFloat(foo) ) {
  console.log(!parseFloat(foo));
}

var baz = [];

if ( baz ) {
  console.log(baz);
}

if ( baz.length ) {
 console.log(baz.length);
}

Falsy Values

false
null
undefined
''
0
NaN
void 0

function giveMeAName(options) {
  var name = (options && options.name) || 'Charlie';
  console.log(name);
}
 
giveMeAName({ name: 'March' });
giveMeAName({});
giveMeAName({ name: '' });
giveMeAName(null);

Using || and &&

var a = [1, 2, 3, 4];
var b = [1, 2, 3, 4]; 
var c = { x: 1, y: 2, z: 3 };
var d = { x: 1, y: 2, z: 3 }; 
var e = "hello";
var f = "he" + "llo"; 
 
console.log((a == b));
console.log((a === b));
 
console.log((c == d));
console.log((c === d));
 
console.log((e == f));
console.log((e === f));

var a = [1,2,3,4];
var b = [1,2,3,4];
var c = a;

console.log(a === b);
console.log(a === c);

Operators

var number = 1,
  string = "1",
  bool = false;

number;
number + "";

string;
+string;
+string++;
string;

bool;
+bool;
bool + "";

var number = 1,
  string = "1",
  bool = true;

string === number;
string === number + "";
+string === number;

bool === number;
+bool === number;
bool === string;
bool === !!string;

var array = [ "a", "b", "c" ];

!!~array.indexOf("a");

if ( array.indexOf("a") >= 0 ) {
  console.log(array.indexOf("a"));
}

var num = 2.5;

parseInt( num, 10 );
~~num;
num >> 0;
num >>> 0;

var neg = -2.5;

parseInt( neg, 10 );
~~neg;
neg >> 0;
neg >>> 0;