scopeChain.js

// // there is another variable with foo name in the function too, so a foo variable with undefinde value get intialized in memory component of execution context of this function
// var foo = 1;
// (function() {
//     console.log(foo); //foo variable with undefined value is present memory component of execution context of this function
//     foo = 2; // this function's foo becomes 2
//     console.log(window.foo); //outer/window foo still remains 1
//     console.log(foo); // this function's foo is 2 
//     var foo = 3; // this function's foo becomes 3
//     console.log(foo); // this function's foo is 3
//     console.log(window.foo) //outer/window foo is still  1
// })();



// function print() {
//     console.log("a", a) //it will look for b in its local memory of print function Execution context, if not found, it will look in its parent lexical environment, which is Global Execution context
// }
// print(); //undefined
// var a = 10;
// print();



// function print2() {
//     console.log("b", b)
// }
// // print2(); //error // because let is not hoisted the way var is hoisted
// let b = 20;
// print2();



function print3() {
    var c = 30;
}
console.log("c", c) //error // because c is var and is defined in print3 function, and var is function scoped, so not accessible outside of print3
console.log(this) //undefined