ES2022 (ECMAScript 2022) Features

ES2022 introduced several improvements, including new class features, array and object enhancements, and top-level await.

1. Class Fields and Private Methods

• Public and private fields (# prefix denotes private).
• Private methods and accessors (# for methods and getters/setters).

Example:

class Person {
    name; // Public field
    #age; // Private field

    constructor(name, age) {
        this.name = name;
        this.#age = age;
    }

    #getAge() { // Private method
        return this.#age;
    }

    getInfo() {
        return `${this.name} is ${this.#getAge()} years old`;
    }
}

const alice = new Person("Alice", 25);
console.log(alice.getInfo()); // ✅ "Alice is 25 years old"
// console.log(alice.#age); // ❌ SyntaxError: Private field '#age' must be declared in an enclosing class

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2. Static Class Fields and Methods

• Classes can now define static fields and private static fields.

Example:

class Counter {
    static count = 0; // Public static field
    static #secret = 42; // Private static field

    static increment() {
        this.count++;
    }

    static getSecret() {
        return this.#secret;
    }
}

Counter.increment();
console.log(Counter.count); // ✅ 1
console.log(Counter.getSecret()); // ✅ 42

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3. Object.hasOwn() (Finalized)

• A safer alternative to Object.prototype.hasOwnProperty().

Example:

const obj = { a: 1 };
console.log(Object.hasOwn(obj, "a")); // ✅ true
console.log(Object.hasOwn(obj, "b")); // ✅ false

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4. RegExp Match Indices (/d Flag)

• Provides start and end positions of matches.

Example:

const regex = /hello/d;
const match = regex.exec("hello world");
console.log(match.indices[0]); // ✅ [0, 5] (start and end positions)

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5. Error.cause Property

• Allows errors to store their original cause.

Example:

try {
    throw new Error("Something went wrong", { cause: "Database connection failed" });
} catch (error) {
    console.log(error.message); // ✅ "Something went wrong"
    console.log(error.cause);   // ✅ "Database connection failed"
}

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6. Array.prototype.at()

• Allows negative indexing for arrays and strings.

Example:

const arr = [10, 20, 30];
console.log(arr.at(-1)); // ✅ 30 (last element)

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7. Top-Level await in Modules

• await can be used outside async functions in ES modules.

Example:

const data = await fetch("https://jsonplaceholder.typicode.com/todos/1").then(res => res.json());
console.log(data);

(Works in ES modules, not in CommonJS.)

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