JS Scope

scope.js

// How many globals?
function Person(name) {
  this.name = name;
}

function greeting(person) {
  console.log("Hello " + person.name);
}

var roger = new Person("Roger");
greeting(roger);


// Creating Scope. How do we create a scope?

var innerState = 12;
console.log(innerState); // should print 12

console.log(innerState); // should print undefined or raise not defined error



// Functions create scope in JS. What if we nest them?
function processData(data) {
  data.forEach(processItem);

  function processItem(item) {
    var reversed = item.split("").reverse().join("");
    console.log(reversed);
  }
}

processData(["Apple", "Orange", "Pear"]);
processData("Peach");



// Can we have more than one variable by the same name?
// This is called shadowing.
var city = "Chicago";

// ?
  var city = "NYC";
  console.log(city) // should print 'NYC'
// ?

console.log(city) // should print 'Chicago'


// this

console.log(this);

function firstFunction() {
  console.log("Hello World!");
  console.log(this);
}

function Person() {
  this.name = "Jane Doe";
  console.log(this);
}

Person.prototype.save = function() {
  $.post("/people", {name: this.name}, function(resp) {
    this.id = resp.id;
  }, "json");
}

firstFunction.apply(new Person());

// hoisting
function hoisted() {
  console.log(name);

  var name = "Roger";
}


// Wacky Stuff ahead...execution contexts with functions
//
function makeCounter() {
  // `i` is only accessible inside `makeCounter`.
  var i = 0;
  return function() {
    console.log( ++i );
  };
}

// Note that `counter` and `counter2` each have their own scoped `i`.
var counter = makeCounter();
counter(); // logs: 1
counter(); // logs: 2

var counter2 = makeCounter();
counter2(); // logs: 1
counter2(); // logs: 2

// IIFE Immediately Invoked Function Expressions
var elems = $('a');
for(var i=0; i<elems.length; i++) {
  $(elems[i]).on('click', function(e){
    e.preventDefault();
    alert( 'I am link #' + i );
  });
}