const str = 'JavaScript';
const result1 = str.slice(-6, -2);
const result2 = str.substring(-6, -2);
const result3 = str.substr(-6, 4);
const combined = [result1, result2, result3];
const final = combined.map(s => s || 'empty').join(' | ');
console.log(final);

const user = {
  name: 'Sarah',
  age: 28,
  city: 'Boston'
};

const keys = Object.keys(user);
const values = Object.values(user);
const entries = Object.entries(user);

const result = entries.map(([key, value]) => {
  return typeof value === 'string' ? key.toUpperCase() : value * 2;
});

console.log(result);