Node benchmark: plain ReadableStream vs. asyncIterator

iterator.js

const { Readable } = require('stream');

const ITEM_COUNT = 10 * 1000 * 1000;

class EventStream extends Readable {
    constructor(count) {
        super({ objectMode: true });
        this.remainingCount = count;
    }

    _read(_size) {
        let result = true;
        do {
            result = this.push({ countdown: this.remainingCount });
            this.remainingCount = this.remainingCount - 1;
        } while (result === true && this.remainingCount > 0);
        if (this.remainingCount === 0) {
            this.push(null);
        }
    }
}

// Stream + AsyncIterator: takes 4.3s on my machine

const start1 = process.hrtime.bigint();
const myStream = new EventStream(ITEM_COUNT);
let processedItems = 0;

(async function() {
    for await (item of myStream) {
        processedItems += 1;
    }
    const end1 = process.hrtime.bigint();
    console.log('Iterator-based: processed %d, elapsed %d ns', processedItems, end1 - start1);
})();

stream.js

const { Readable } = require('stream');

const ITEM_COUNT = 10 * 1000 * 1000;

class EventStream extends Readable {
    constructor(count) {
        super({ objectMode: true });
        this.remainingCount = count;
    }

    _read(_size) {
        let result = true;
        do {
            result = this.push({ countdown: this.remainingCount });
            this.remainingCount -= 1;
        } while (result === true && this.remainingCount > 0);
        if (this.remainingCount === 0) {
            this.push(null);
        }
    }
}

// Stream only - takes 1.4s on my machine:

const start1 = process.hrtime.bigint();
const myStream = new EventStream(ITEM_COUNT);
let processedItems = 0;
myStream.on('data', function() {
    processedItems += 1;
});
myStream.on('end', function() {
    const end1 = process.hrtime.bigint();
    console.log('Stream-only: processed %d, elapsed %d ns', processedItems, end1 - start1);
});

Note: benchmark performed with Node 15.10.0 installed via nvm, on Debian 10.7 amd64 running on Intel Core i7-5500U.