let a_string = "any string";
let a_boolean = true;
let a_undefined = undefined;
let a_null = null;

let a_string_1;
let a_boolean_1;
let a_undefined_1;
let a_null_1;

let first_name = "tran";
let last_name = "hoang";
let country = "viet nam";
let age = 22;

let first_name_1 = first_name,
    last_name_1 = last_name,
    country_1 = country,
    age_1 = age;

let myAge = 22;
let yourAge = 30;