tekaratzas

// Adding a property to the global Object => all objects inherit from this. ex: toString method and prototype.
Object.prototype.WTF = "this should not be in your object";

function a() {
  this.unwanted = 10;
  this.crap = "dhjbjbfdjbf";
}

function child() {
  this.a = 1;

tekaratzas

(
  // evaluate the function in the parenthesis
  function(){}
  // return the evaluated function object
)() // call it immediately

// The same functionality can be done as follows;
!function(){}()
+function(){}()
(function(){}());

tekaratzas

var foo = 12;

function changeFoo() {
  foo = 34; // changes global scope and not local scope!
}

changeFoo();

console.log(foo);

tekaratzas

function test() {
  this.arr = [1,2,4];
  this.message = "I am here";
  this.fun = function() {
  	this.arr.forEach(function(item) {
    	console.log(this.message); // will print undefined 3 times since this refers to the global object
    });
  }
}

tekaratzas

// 1
console.log(this); // refers to the Global Object aka window
// its methods include prompt alert confirm etc...

// 2
function test() {
  console.log(this);
  this.method = function inner() {console.log(this)};
}; // Here again "this" will refer to the global object
test();

tekaratzas

console.log(typeof "foo" === "string"); //true 
console.log(typeof String("foo") === "string"); // true
console.log(typeof new String("foo") === "string"); // false
console.log(typeof 1.2 === "number"); //true
console.log(typeof new Date() === "Date"); //false Date is an Object
console.log(typeof [1,2,3] === "array"); //false, an array is on object!

/** Proper way to test type of object **/

function is(type, obj) {

tekaratzas

// examples with ==

1 == "1" // true
"/t" == 0 // true
"34" == 2 // false
new Number(10) == 10 // true
Number(10) === 10 //true

// examples with ===

tekaratzas

/**
  Here, the parser will add a semi colon after return causing the function to return undefined.
**/
function test(){
  var name = "Hello";
  return // it will add a ; here
  {
    name: name
  }
}