async-iterator-stream

demo.js

async function* source(){
  let n = 1;
  while(true){
    yield n++;
    await new Promise(res => setTimeout(res, 100));
  }
}

async function* map(func){
  for await(const chunk of this){
    yield await func(chunk);
  }
}

async function* take(count){
  for await(const chunk of this){
    if(count-- <= 0) break;
    yield chunk;
  }
}

async function reduce(func, initial){
  for await(const chunk of this){
    initial = func(initial, chunk);
  }
  return initial;
}

async function run(){
  console.log('start');
  const result = await source()
    ::map(t => t*2)
    ::take(3)
    ::reduce((a, b) => a+b, 0);
  console.log('done', result);
}

run()