JavaScript New Features 2025: Everything New in ECMAScript 2024 (ES15)

 

As of May 2025, JavaScript has evolved with several new features introduced in ECMAScript 2024 (ES15). These enhancements aim to improve code readability, performance, and developer productivity. Here’s a comprehensive overview:

🚀 ECMAScript 2024 (ES15) – Key Features

1. Array Grouping Methods

• Object.groupBy() and Map.groupBy(): Group elements of an iterable based on a callback function.

const numbers = [1, 2, 3, 4, 5, 6];

const grouped = Object.groupBy(numbers, n => (n % 2 === 0 ? 'even' : 'odd'));

console.log(grouped); // { odd: [1, 3, 5], even: [2, 4, 6] }

2. Promise.withResolvers()

Simplifies the creation of promises by providing the promise along with its resolve and reject functions.

const { promise, resolve, reject } = Promise.withResolvers();

// Use resolve() or reject() as needed

3. Resizable and Transferable ArrayBuffers

Enhances ArrayBuffer and SharedArrayBuffer by allowing in-place growth and shrinking, improving memory management. 

4. Regular Expressions with the /v Flag

Introduces the /v flag for regular expressions, enabling advanced features like set notation and properties of strings. 

5. Atomics.waitAsync()

Allows asynchronous waiting on shared memory locations, facilitating non-blocking synchronization in concurrent environments. 

6. String Well-Formedness Methods

• String.prototype.isWellFormed(): Checks if a string contains only well-formed Unicode.
• String.prototype.toWellFormed(): Returns a well-formed version of the string, replacing lone surrogates. 

7. Immutable Array Methods

Introduces non-mutating array methods:

• toReversed(): Returns a reversed copy of the array.
• toSorted(): Returns a sorted copy of the array.
• toSpliced(): Returns a copy with spliced elements.
• with(): Returns a copy with a value replaced at a specified index. 

8. Top-Level await

Allows the use of await at the top level of modules, simplifying asynchronous code.

const data = await fetchData();

9. Pipeline Operator (|>)

Introduces a new syntax for function chaining, improving code readability.

const result = value |> double |> square |> increment;

10. Records and Tuples (Proposed)

Immutable data structures that offer value-based equality:

• Records: Immutable key-value pairs.
• Tuples: Immutable ordered lists. 

11. Decorators (Proposed)

Provide a way to add annotations and meta-programming syntax for class declarations and members.

12. Decimal Data Type (Proposed)

Introduces a Decimal type for precise decimal arithmetic, addressing floating-point inaccuracies.

These features collectively enhance JavaScript’s capabilities, making it more robust and developer-friendly. While some features are finalized, others are still in the proposal stage and may be included in future ECMAScript versions.