Node.js 11.x: What's New, Release History & Support Lifecycle

What Is New in Node.js 11?

Array.flat(), flatMap(), and Object.fromEntries()

Three often-requested array and object utilities land natively in Node.js 11 via V8 7.0.

// flat() -- flatten nested arrays
[1, [2, [3]]].flat();      // [1, 2, [3]]
[1, [2, [3]]].flat(Infinity); // [1, 2, 3]

// flatMap() -- map + one-level flatten in one pass
['hello world', 'foo'].flatMap(s => s.split(' ')); // ['hello', 'world', 'foo']

// Object.fromEntries() -- reverse of Object.entries()
const map = new Map([['a', 1], ['b', 2]]);
Object.fromEntries(map); // { a: 1, b: 2 }

Async Iteration for Readable Streams

Node.js 11 adds for await...of support for readable streams. This lets you consume streaming data with clean async iteration instead of event listeners.

import { createReadStream } from 'node:fs';

const stream = createReadStream('./large.csv', { encoding: 'utf8' });
for await (const chunk of stream) {
  processChunk(chunk);
}

Backpressure is still handled automatically. This is a more readable pattern for sequential stream processing.

Full ICU by Default

Node.js 11 bundles full ICU data on all platforms by default. Prior to this, the default build only included a small subset of locales. Full ICU means Intl APIs (date formatting, number formatting, collation) work correctly for all locales without building a custom Node.js binary.