Variable Declarations in JavaScript — http://bit.ly/js-vars

# Variables Intro.md

Six types of Variable Declarations in JavaScript

— by Abhisek Pattnaik <[email protected]>

Variable Declarations.md

Variable Declarations

1. function param
   implicit local variable declaration

   function sum(num) {
     // `num` is a local variable
   }

2. using var keyword
   explicit local variable declaration inside a function

   function getMe() {
    var answer = 'no';
   }

   or implicit global variable declaration when declared out of any function context

   var age = 150; // global

3. using const keyword (similar to let)
   implicit global variable declaration when declared out of any function context

   const name = 'Abhisek';

4. without using var, const or let keywords (JS being overfriendly)
   implicitly creates a global variable (bad!!!) ⚠️ (doesn't work in strict mode) 👿

   function me() {
    answer = 'Abhisek';
   }
   me();
   console.log(answer) //=> 'Abhisek'

5. using let keyword
   explicit local variable declaration inside a function

   function person() {
    let age = 123;
   }

   or implicit global variable declaration when declared out of any function context

   let gender = 'male';

6. assigning as a property to global object e.g. window object
   explicit global variable creation

   window.applicationName = 'TrimmerApp';
   console.log(applicationName); //=> 'TrimmerApp'