let-const-scope.js

/* let, const */
let gf = "Jennifer Lawrence";
console.log(gf);
gf = "Elizabeth Olsen";
console.log(gf);

/**
 * Output :
 Jennifer Lawrence
 Elizabeth Olsen
*/

const username = "willsmith";
username = "jhonshow"; //TypeError: Assignment to constant variable.

const number = [1, 2, 3, 4, 5];
number[1] = 10;
number.push(6);
console.log(number);
// Output: [ 1, 10, 3, 4, 5, 6 ]

const user = { name: "Shakib", age: 30 };
user.name = "Mushfiq";
user.profession = "Cricker";
console.log(user);
// Output: { name: 'Mushfiq', age: 30, profession: 'Cricker' }

/* Block Scope */
let sum = 0;
for (let i = 0; i < 5; i++) {
	sum += i;
}
console.log(sum); // 10
console.log(i);
//ReferenceError: i is not defined