// In a module file
const response = await fetch("https://api.example.com/data");
const data = await response.json();

export { data };

// Can be used in other modules
import { data } from "./data.js";
console.log(data);

Class Fields

Declare class fields directly in the class body without constructor.

class Person {
  // Public fields
  name = "John";
  age = 30;
  
  // Private fields
  #secret = "private data";
  
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  
  getSecret() {
    return this.#secret;
  }
}

const person = new Person("Jane", 25);
console.log(person.name); // "Jane"
console.log(person.getSecret()); // "private data"

Array.prototype.at

Access array elements using negative indices (counting from the end).

const arr = [1, 2, 3, 4, 5];

console.log(arr.at(0)); // 1 (first element)
console.log(arr.at(-1)); // 5 (last element)
console.log(arr.at(-2)); // 4 (second to last)
console.log(arr.at(10)); // undefined (out of bounds)

// Useful for getting last element
const last = arr.at(-1); // Better than arr[arr.length - 1]

Object.hasOwn

Safe way to check if an object has a property as its own property.

const obj = { a: 1 };

console.log(Object.hasOwn(obj, "a")); // true
console.log(Object.hasOwn(obj, "b")); // false
console.log(Object.hasOwn(obj, "toString")); // false (inherited)

// Safer than hasOwnProperty
const obj2 = Object.create(null);
obj2.a = 1;

// This would throw an error:
// obj2.hasOwnProperty("a");

// This works:
console.log(Object.hasOwn(obj2, "a")); // true