Hoisted concept in javascript

Another unusual thing about variables in JavaScript is that you can refer to a variable declared later, without getting an exception. This concept is known as hoisting. Variables in JavaScript are in a sense “hoisted” or lifted to the top of the function or statement. However, variables that are hoisted will return a value of undefined. So even if you declare and initialize after you use or refer to this variable, it will still return undefined.

 
/**
 * Example 1
 */

console.log(x === undefined); // true

var x = 3;

/**
 * Example 2
 */

// will return a value of undefined

var myvar = "my value";
 
(function() {
  console.log(myvar); // undefined
  var myvar = "local value";
})();

One Important things to remember is Only function declaration gets hoisted to the top and not the function expression.

 

/* Function declaration */ 

HoistedFun(); // "I am hoisted" 

function HoistedFun() {
    console.log("I am hoisted");
} /* Function expression */ 

FunctionExp(); // TypeError:FunctionExp is not a 

function var FunctionExp = function() {
 console.log("Hoisetd");
};