ECMAScript 2026
New Features in JavaScript 2026
| Feature | Description |
|---|---|
| Error.isError() | Checks whether a value is an Error object |
| Array.fromAsync() | Copies items from async iterables into a new array |
| The using keyword | Declares block-scoped variables synchronously disposed |
| await using | Automatic cleanup of resources |
| Uint8Array fromBase64() | Creates a Uint8Array object from a base64-encoded string |
| Uint8Array toBase64() | Returns a base64-encoded string from the data in an int8Array |
| Uint8Array fromHex() | Creates a Uint8Array object from a hexadecimal string |
| Uint8Array toHex() | Returns a hex-encoded string from the data in an int8Array |
Warning
The 2026 edition is not published yet. It normally ships in June.
As of November 2025, this is a list of the features in the draft, that is likely to be in the ES2026.
Error.isError()
The Error.isError() static method checks whether a value is an Error object.
Example
Error.isError(new TypeError()); // true
Error.isError({ name: "Error" }); // false
Try it Yourself »
Error.isError() is a safe alternative to
instanceof Error which fails across realms.
Realm-safe error check:
An Error from an iframe verifies with Error.isError()
and fails with instanceof.
Browser Support
Error.isError() is already supported in many browsers:
| Chrome 134 |
Edge 134 |
Firefox 138 |
Safari ❌ |
Opera 119 |
| Mar 2025 | Mar 2025 | Apr 2025 | ❌ | May 2025 |
Array.fromAsync()
Example
async function* asyncGenerator() {
yield Promise.resolve(1);
yield Promise.resolve(2);
yield Promise.resolve(3);
}
async function processAsyncData() {
const arr = await Array.fromAsync(asyncGenerator());
}
processAsyncData();
Try it Yourself »
Browser Support
Array.fromAsync() is already supported in many browsers:
| Chrome 121 |
Edge 121 |
Firefox 115 |
Safari 16.4 |
Opera ❌ |
| Jan 2024 | Jan 2024 | Jul 2023 | May 2023 | ❌ |
Uint8Array to/fromBase64()
Examples
let string = 'W3Schools 123';
const arr = Uint8Array.fromBase64(string);
Try it Yourself »
const arr = new Uint8Array([91,116,156,134,138,37,179,93,183]);
let text = arr.toBase64();
Try it Yourself »
Browser Support
to/fromBase64() is already supported in many browsers:
| Chrome 140 |
Edge 140 |
Firefox 133 |
Safari 18.2 |
Opera ❌ |
| Sep 2025 | Sep 2025 | Nov 2024 | Des 2024 | ❌ |
Uint8Array to/fromHex()
Examples
let text = '5b749c868a25b35db7';
const arr = Uint8Array.fromHex(text);
Try it Yourself »
const arr = new Uint8Array([91,116,156,134,138,37,179,93,183]);
let text = arr.toHex();
Try it Yourself »
Browser Support
to/fromHex() is already supported in many browsers:
| Chrome 140 |
Edge 140 |
Firefox 133 |
Safari 18.2 |
Opera ❌ |
| Sep 2025 | Sep 2025 | Nov 2024 | Des 2024 | ❌ |
Explicit Resource Management
The using Keyword
The using keyword is an addition to JavaScript 2026.
It provides a mechanism for managing resources that require explicit disposal.
It declares a block-scoped variable, similar to const, but with the difference that
it guarantees synchronous disposal of the used resource when the variable goes out of scope.
Example
class MyResource {
constructor(name) {
this.name = name;
myDisplay(`Resource ${this.name} acquired.`);
}
[Symbol.dispose]() {
myDisplay(`Resource ${this.name} disposed.`);
}
}
function manageResource() {
using resource = new MyResource("Database Connection");
// Use the resource here
myDisplay(`Using resource: ${resource.name}`);
}
Try it Yourself »
The using keyword simplifies resource management by automatically
handling the cleanup process, reducing the risk of resource leaks and improving code readability
compared to manual try...finally blocks for disposal.
Resource Management
usingis designed for objects that implement theSymbol.disposemethod, which defines the cleanup logic for the resource.Synchronous Disposal
When a variable declared withusingexits its scope (at the end of a block or function), itsSymbol.disposemethod is automatically called.Asynchronous Disposal
For resources requiring asynchronous cleanup, theawait usingdeclaration can be employed. This ensures that the disposal process is awaited before the variable fully goes out of scope.Block-Scoped
Likeconst, variables declared withusingare local to the block in which they are declared, and must be initialized at the time of declaration.Immutable
Like toconst, variables declared withusingcannot be reassigned after initialization.
Browser Support
using is already supported in many browsers:
| Chrome 134 |
Edge 134 |
Firefox 141 |
Safari ❌ |
Opera 119 |
| Mar 2025 | Mar 2025 | Jul 2025 | ❌ | May 2025 |
Explicit Resource Management
await using
Inspired by other languages, JavaScript 2026 introduces using blocks for automatic cleanup
of resources like file handles, database connections, or network streams.
This is especially beneficial for asynchronous operations:
Example
async function processFile() {
using fileHandle = await openFile('data.txt');
// Work with fileHandle here
} // fileHandle is automatically closed here
Try it Yourself »
Browser Support
await using is already supported in many browsers:
| Chrome 134 |
Edge 134 |
Firefox 141 |
Safari ❌ |
Opera 119 |
| Mar 2025 | Mar 2025 | Jul 2025 | ❌ | May 2025 |
