Demonstration of queuing strategy for Streams API

webStreamsQueuingStrategy.js

// Demonstration of queuing strategy for Streams API
// $ node  ./webStreamsQueuingStrategy.js

export { }; // Intentional unused export to force "type: module" on .js file

// These strategies are equivalent
const basicStrategy = {
  highWaterMark: 3, // If no .size() specified, default is .size() === 1 (CountQueuingStrategy)
  // size(chunk) { return 1; } // Implied
};
const chunkStrategy = new CountQueuingStrategy({
  highWaterMark: 3
});
const elementsStrategy = {
  highWaterMark: 3 * 4, // Assuming each chunk is a JSON array with exactly 4 elements
  size(chunk) { return JSON.parse(chunk).length }
}
const strategies = [basicStrategy, chunkStrategy, elementsStrategy];

const chunk = JSON.stringify(['a', 'b', 'c', 'd']);

for (const strategy of strategies) {
  let i = 0;
  const stream = new ReadableStream({
    pull(controller) {
      if (i > 4) {
        controller.close();
      }
      else {
        controller.enqueue(chunk);
        console.log(`enqueued ${i}`);
        i++;
      }
    }
  }, strategy);
  
  for await (const _ of stream) {
    console.log('sink');
  }

  console.log('---------------------------');
}