const a = {};
const b = { key: 'b' };
const c = { key: 'c' };

a[b] = 123;
a[c] = 456;

console.log(a[b]);

const obj = {
  a: 1,
  b: function() {
    return this.a;
  }
};
const b = obj.b;
console.log(b());

const regex = /\D+/;
const str = '123abc456';
console.log(str.match(regex)[0]);

const regex = /^cat/gm;
const str = `dog
cat
bat`;
console.log(str.match(regex));

const a = {};
const b = {};
console.log(a == b);
console.log(a === b);

try {
  throw new Error('Error');
} catch (e) {
  console.log(e.message);
} finally {
  console.log('Finally');
}

const arr = [1, 2, 3];
arr[10] = 4;
console.log(arr.length);

const getItems = (fruitList, ...args, favoriteFruit) => 
[...fruitList, ...args, favoriteFruit]

getItems(["banana", "apple"], "pear", "orange")

const numbers = [10, 20, 30, 40];
const [a] = numbers;

console.log(a);

const baseObject = {x: 1, y: 2};
const extendedObject = {...baseObject, z: 3};
const result = { ...extendedObject, x: 4 };

console.log(result);