!Roricchi 2.0『藤田の妻』•2y ago

How to stop reading from a ReadableStream?

let user

for await (const data of readable) {
  if (data.user.id === 'user-id') {
    user = data

    break
  }
}

console.log(user)

let user

for await (const data of readable) {
  if (data.user.id === 'user-id') {
    user = data

    break
  }
}

console.log(user)

the break stops the for loop, but it doesnt exit? because it only logs the user after the readable stream is completed. i dont want to wait for the stream to complete/end, i want to get user immidiately after break is called. here readable is ReadableStream

1 Reply

jeff.hykin•2y ago

In this case you probably need to do manual iteration instead of using a for-of loop. See an example here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Iterators_and_Generators I imagine it'll be like the following but with some await's

const it = makeRangeIterator(1, 10, 2);

let result = it.next();
while (!result.done) {
 console.log(result.value); // 1 3 5 7 9
 result = it.next();
}

console.log("Iterated over sequence of size: ", result.value); // [5 numbers returned, that took interval in between: 0 to 10]

const it = makeRangeIterator(1, 10, 2);

let result = it.next();
while (!result.done) {
 console.log(result.value); // 1 3 5 7 9
 result = it.next();
}

console.log("Iterated over sequence of size: ", result.value); // [5 numbers returned, that took interval in between: 0 to 10]

Iterators and generators - JavaScript | MDN

Iterators and Generators bring the concept of iteration directly into the core language and provide a mechanism for customizing the behavior of for...of loops.