25 Must‑Know ES202x Features to Supercharge Your JavaScript Code

JavaScript, as one of the most popular programming languages, continuously evolves through the ECMAScript standard, bringing many practical new features. Below are 25 ES features that can significantly improve coding efficiency, making code cleaner, more elegant, and more performant.

1. Optional Chaining

Eliminate cumbersome null checks with the ?. operator for safe property access.

// Previous syntax
const street = user && user.address && user.address.street;

// New syntax
const street = user?.address?.street;

2. Nullish Coalescing

Use the ?? operator to provide default values for null or undefined.

const value = null;
const defaultValue = value ?? 'default'; // 'default'

3. Private Class Fields

Declare private fields with # to enhance encapsulation in OOP.

class Person {
  #name;
  constructor(name) {
    this.#name = name;
  }
  getName() {
    return this.#name;
  }
}

4. Dynamic Import

Load modules on demand to optimize application performance.

button.addEventListener('click', async () => {
  const module = await import('./feature.js');
  module.doSomething();
});

5. Array.prototype.flat() and flatMap()

Easily handle nested arrays.

const nested = [1, [2, 3], [4, [5, 6]]];
const flattened = nested.flat(2); // [1, 2, 3, 4, 5, 6]

6. Object Literal Enhancements

More concise property and method definitions.

const name = 'Tom';
const age = 18;
const person = {
  name,
  age,
  sayHi() {
    console.log('Hi!');
  }
};

7. Promise.allSettled()

Wait for all promises to settle, regardless of outcome.

const promises = [
  fetch('/api/1'),
  fetch('/api/2'),
  fetch('/api/3')
];
const results = await Promise.allSettled(promises);

8. BigInt

Handle integers larger than the safe Number range.

const bigNumber = 9007199254740991n;
const result = bigNumber + 1n;

9. globalThis

A unified way to access the global object across environments.

console.log(globalThis);

10. String.prototype.matchAll()

More powerful string matching capabilities.

const str = 'test1test2test3';
const regexp = /test(\d)/g;
const matches = [...str.matchAll(regexp)];

11. Logical Assignment Operators

Simplify conditional assignments.

// Logical AND assignment
x &&= y; // equivalent to x && (x = y)

// Logical OR assignment
x ||= y; // equivalent to x || (x = y)

// Nullish coalescing assignment
x ??= y; // equivalent to x ?? (x = y)

12. Promise.any()

Returns the first fulfilled promise.

const promises = [
  fetch('/api/1'),
  fetch('/api/2'),
  fetch('/api/3')
];
try {
  const first = await Promise.any(promises);
  console.log(first);
} catch (error) {
  console.log('All promises rejected');
}

13. Numeric Separators

Improve readability of large numbers.

const billion = 1_000_000_000;
const bytes = 0xFF_FF_FF_FF;

14. String.prototype.replaceAll()

Replace all occurrences of a substring.

15. WeakRef and FinalizationRegistry

Better memory‑management mechanisms.

16. Top‑Level Await

Use await directly in module scope.

17. Static Initialization Blocks

More flexible initialization of static class members.

18. Array.at()

Intuitive array index access, supporting negative indices.

19. Object.hasOwn()

Safer property existence checking.

20. Error Cause

Better error tracing with a cause property.

21. Object.groupBy()

Group array elements by a criterion.

22. RegExp Named Capture Groups

Clearer regex match results with named groups.

23. Promise.withResolvers()

More elegant control over Promise resolution.

24. Array Copy Methods

Convenient non‑mutating array operations.

const arr = [1, 2, 3];
const copy = arr.toReversed(); // does not modify original
const sorted = arr.toSorted(); // does not modify original

25. Decorators

Enhance classes and members with reusable behavior.

function logged(target, context) {
  return class extends target {
    exec(...args) {
      console.log('Starting execution...');
      const result = super.exec(...args);
      console.log('Finished execution.');
      return result;
    }
  };
}

@logged
class Example {
  exec() {
    // ...
  }
}

Feel free to add more features.