3_variable.js

var a = 'Hello Wordl' //Before ES6 we used var to declear variable. But in currntly in ES6 or after ES5 we are not using var to devlear variable.
let b = 'This is let javascript variable' //Frome ES6 we used let to declear variable. And we need to used let insted of  var. let variable only run on the scope.
const c = 'This is const javascript variable' //From ES6 we used const to declear constent variable in javascript. And const variable can not re-declear or changed the value.

{
    let b = 'This';
    console.log(b);
}

console.log(a);
console.log(b);
console.log(c);