const regex = /\d+/g;
const str = 'abc123def456';
console.log(regex.test(str), regex.test(str));

const user = { name: 'Alice' };
const { name, age = 25, city = 'NY' } = user;
console.log(age, city);

.list li:first-of-type {
  color: red;
}
.list li:last-of-type {
  color: blue;
}

const numbers = [5, 10, 15, 20];
const index = numbers.findLastIndex(n => n > 12);
console.log(index, numbers[index]);

const arr = [1, NaN, 3];
const found1 = arr.includes(NaN);
const found2 = arr.indexOf(NaN);
console.log(found1, found2);

.card::before {
  content: '★';
  position: absolute;
  top: 10px;
  left: 10px;
}

const items = document.querySelectorAll('.item');
const isArray = Array.isArray(items);
const canMap = typeof items.map === 'function';
console.log(isArray, canMap);

const btn = document.querySelector('.btn');
btn.dataset.id = '123';
btn.dataset.userName = 'Alice';
console.log(btn.getAttribute('data-user-name'));

.container {
  display: flex;
  align-content: space-between;
  flex-wrap: wrap;
  height: 300px;
}

const str = 'JavaScript';
const char1 = str[0];
const char2 = str.charAt(0);
str[0] = 'j';
console.log(str[0], char1 === char2);