Closures & Variable hoisting

// Simple example to show the power of closure when exploited w.r.t scope
function power_of (power) {
  return function (number) {
    return Math.pow(number, power);
  };
}

var power_of_3 = power_of(3),
    power_of_4 = power_of(4);
    
console.log("2^3", power_of_3(2)); // 8
console.log("2^4", power_of_4(2)); // 16

// Example to show how variable hoisting works in JS
var x = 1;
(function () {
  console.log( "Global variable x is accessed in local scope with same value = ", x ); // 1
})();

var x = 1;
(function () {
  x = 2;
  console.log("Because of variable hoisting x is intialized in local scope with value = ", x); // 2
  return;
  function x () {};
})();
console.log("x in global scope remains untouched with value = ", x); // still remains 1

var x = 1;
(function  () {
  var x = x || 2;
  console.log("Because of variable hoisting x is intialized in local scope with value = ", x); // 2
})();
console.log("x in global scope remains untouched with value = ", x); // still remains 1

var x = 1;
(function  () {
  console.log("Because of variable hoisting x is intialized without any values in local scope = ", x); // undefined
  var x;
})();
console.log("x in global scope remains untouched with value = ", x); // still remains 1

var x = 1;
(function  () {
  x = x || 2;
  var x;
  console.log("Because of variable hoisting x is intialized in local scope with value = ", x); // 2
})();
console.log("x in global scope remains untouched with value = ", x); // still remains 1

var x = 1;
(function  () {
  x = x || 2;
  console.log("Since x is not initialized in local scope it picks the one in global scope with value = ", x); // 1
})();
console.log("x in global scope remains untouched with value = ", x); // still remains 1

var x = 1;
(function(){
  console.log("Because of variable hoisting x is intialized without any values in local scope = ", x); // undefined
  return;
  var x;
})();
console.log("x in global scope remains untouched with value = ", x); // still remains 1

// Private variables can be set in JS using closures
function Dog () {
  var no_of_times_barked = 0;
  this.bark = function () {
    console.log("Woof");
    no_of_times_barked++;
  };
  this.getNoOfTimesBarked = function  () {
    return no_of_times_barked;
  };
}

var dog = new Dog();
console.log("No of times barked = ", dog.getNoOfTimesBarked());
dog.bark();
console.log("No of times barked = ", dog.getNoOfTimesBarked());