Node.js - Simple Stream and Generator Demos

Simple Stream.

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

// Reader

const createCounterReader = () => {

let count = 0;

return new Readable({

objectMode: true,

read () {

count += 1;

console.log('reading:', count);

this.push(count);

}

});

};

const counterReader = createCounterReader();

// Writer

const logWriter = new Writable({

objectMode: true,

write: (chunk, _, done) => {

setTimeout(() => {

console.log('writing:', chunk);

done();

}, 100);

}

});

// Pipe reader to Writer

counterReader.pipe(logWriter);


Stream for async counter.

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

const createCounterReader = (delay) => {

let counter = 0;

const reader = new Readable({

objectMode: true,

read () {}

});

setInterval(() => {

counter += 1;

console.log('reading:', counter);

reader.push(counter);

}, delay);

return reader;

};

const counterReader = createCounterReader(1000);

const logWriter = new Writable({

objectMode: true,

write: (chunk, _, done) => {

console.log('writing:', chunk);

done();

}

});

counterReader.pipe(logWriter);

Stream for async counter writer.

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

const createCounterReader = (delay) => {

let counter = 0;

const reader = new Readable({

objectMode: true,

read () {}

});

setInterval(() => {

counter += 1;

console.log('reading:', counter);

reader.push(counter);

}, delay);

return reader;

};

const counterReader = createCounterReader(1000);

const logWriter = new Writable({

objectMode: true,

write: (chunk, _, done) => {

setTimeout(() => {

console.log('writing:', chunk);

done();

}, 5 * 1000);

}

});

counterReader.pipe(logWriter);

Simple Generator Sync.

function* counterGenerator() {

let count = 0;

while (true) {

count += 1;

console.log('reading:', count);

yield count;

}

}

const counterIterator = counterGenerator();

const logIterator = (iterator) => {

for (const item of iterator) {

console.log('writing:', item);

}

};

logIterator(counterIterator);

Simple Generator Async.

function* counterGenerator() {

let count = 0;

while (true) {

count += 1;

console.log('reading:', count);

yield count;

}

}

const counterIterator = counterGenerator();

const logIterator = async (iterator) => {

for (const item of iterator) {

await new Promise((resolve, reject) => {

setTimeout(() => {

resolve();

}, 100);

});

console.log('writing:', item);

}

};

logIterator(counterIterator);


Async Generator Counter.

async function* counterGenerator(delay) {

let counter = 0;

while (true) {

await new Promise(r => setTimeout(r, delay));

counter += 1;

console.log('reading:', counter);

yield counter;

}

}

const counterIterator = counterGenerator(1000);

const logIterator = async (iterator) => {

for await (const item of iterator) {

console.log('writing:', item);

}

};

logIterator(counterIterator);

Async Generator Counter for Async Interator.

async function* counterGenerator(delay) {

let counter = 0;

while (true) {

await new Promise(r => setTimeout(r, delay));

counter += 1;

console.log('reading:', counter);

yield counter;

}

}

const counterIterator = counterGenerator(1000);

const logIterator = async (iterator) => {

for await (const item of iterator) {

console.log('writing:', item);

await new Promise(r => setTimeout(r, 5 * 1000));

}

};

logIterator(counterIterator);