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How to use the asyncMap function from pull-stream

Find comprehensive JavaScript pull-stream.asyncMap code examples handpicked from public code repositorys.

pull-stream.asyncMap is a function in the pull-stream library that applies an asynchronous transformation to each item in a pull-stream.

index.js

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let recordStream
if (seqStream) {
  recordStream = pull(
    seqStream,
    pull.asyncMap((seq, cb) => {
      ensureIndexSync({ data: { indexName: 'seq' } }, () => {
        getRecord(seq, cb)
      })
    })

core.js

GitHub: ssbc/ssb-db2

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  where(author(feedId)),
  asOffsets(),
  batch(1000),
  toPullStream()
),
pull.asyncMap(log.del),
pull.onEnd((err) => {
  // prettier-ignore
  if (err) return cb(new Error('deleteFeed() failed for feed ' + feedId, {cause: err}))

+ 49 other calls in file

How does pull-stream.asyncMap work?

pull-stream.asyncMap works by taking two arguments: a function that performs an asynchronous transformation on each item in the pull-stream, and a pull-stream source. The function creates a new pull-stream that is a copy of the source stream, but with the asynchronous transformation applied to each item in the stream. To achieve this, pull-stream.asyncMap uses a pull-stream through that wraps the original source stream and applies the asynchronous transformation using a callback function. The asynchronous transformation function takes two arguments: the item from the original source stream, and a callback function that is used to pass the transformed item to the next stage of the pull-stream. The function must call the callback function when it is finished transforming the item, or else the pull-stream will become stuck and not progress. pull-stream.asyncMap is useful when you need to apply an asynchronous transformation to each item in a pull-stream. For example, you might use pull-stream.asyncMap to transform a stream of text data into a stream of parsed JSON objects, or to make an API call for each item in the stream and return the results. Note that pull-stream.asyncMap is a part of the pull-stream library, which is a streaming library for Node.js and the browser. It is designed to work with other pull-stream functions to create powerful and flexible stream processing pipelines.

migrate.js

GitHub: ssbc/ssb-db2

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pull(
  oldLog.getStream({ gt: migratedOffset }),
  pull.map(updateMigratedSizeAndPluck),
  pull.map(toBIPF),
  pull.asyncMap(writeToNewLog),
  (drainAborter = config.db2.maxCpu
    ? drainGently(tooHotOpts(config), op, opDone)
    : pull.drain(op, opDone))
)

index.js

GitHub: ssbc/ssb-db2

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}

startMeasure(t, 'add 1000 box1 msgs')
pull(
  pull.values(contents),
  pull.asyncMap(sbot.db.publish),
  pull.collect((err, msgs) => {
    endMeasure(t, 'add 1000 box1 msgs')
    if (err) t.fail(err)

+ 3 other calls in file

Ai Example

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const pull = require("pull-stream");
const fetch = require("node-fetch");

// Define a pull-stream source
const source = pull.values(["apple", "banana", "orange"]);

// Define an asynchronous transformation function
async function getLength(item) {
  const response = await fetch(`https://api.example.com/length/${item}`);
  const json = await response.json();
  return json.length;
}

// Create a new pull-stream with the asynchronous transformation applied
const transformedStream = pull(source, pull.asyncMap(getLength));

// Consume the transformed stream
pull(transformedStream, pull.log());

In this example, we start by importing the pull-stream library and the node-fetch library, which is used to make HTTP requests. We then define a pull-stream source called source that contains three strings: 'apple', 'banana', and 'orange'. Next, we define an asynchronous transformation function called getLength. The function takes an item from the source stream and makes an API call to retrieve the length of the item from a hypothetical API. The function returns the length as a promise. We then use pull.asyncMap to create a new pull-stream called transformedStream that applies the getLength function to each item in the source stream. Finally, we use pull.log to consume the transformedStream and log each transformed item to the console. The output shows the length of each string in the source stream, as retrieved from the hypothetical API. Note that this is just an example, and the actual transformation function will depend on the specific use case. However, the basic pattern of using pull.asyncMap to apply an asynchronous transformation to each item in a pull-stream is the same.

index.js

GitHub: ssbc/ssb-tribes2

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}

function listInvites() {
  return pull(
    pull.values([0]), // dummy value used to kickstart the stream
    pull.asyncMap((n, cb) => {
      ssb.metafeeds.findOrCreate((err, myRoot) => {
        // prettier-ignore
        if (err) return cb(clarify(err, 'Failed to get root metafeed when listing invites'))

+ 32 other calls in file

reactive.html

GitHub: juliangruber/level-list

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      value : e.value,
      type  : e.value == null ? 'del' : 'put'
    }
  }),
  pw.recent(opts.windowSize, opts.windowTime),
  pull.asyncMap(function (batch, cb) {
    db.batch(batch, cb)
  }),
  pull.drain(null, done)
)

+ 3 other calls in file

ssb-server.js

GitHub: planetary-social/planetary-graphql

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),
pull.filter(m => (
  m.value.author === m.value.content.about &&
  m.value.content.image
)),
pull.asyncMap((m, cb) => ssb.aboutSelf.get(m.value.author, cb)),
pull.drain(about => {
  if (about.image) {
    ssb.blobs.has(about.image, (err, hasBlob) => {
      if (err) return console.warn(err)

meta-feed-helpers.js

GitHub: ssbc/ssb-tribes2

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pull.filter(
  (rootMsg) => rootMsg.value.content?.tangles?.group?.root === null
),

// see if there are and members added
pull.asyncMap((rootMsg, cb) => {
  // return rootMsg if empty group, otherwise return false
  let foundMember = false
  pull(
    ssb.db.query(

+ 2 other calls in file

format.js

GitHub: ssbc/ssb-box2

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}

function listGroupIds(opts = {}) {
  return pull(
    pull.values([0]),
    pull.asyncMap((_, cb) => {
      keyringReady.onReady(() => {
        return cb(null, keyring.group.list({ live: !!opts.live }))
      })
    }),

+ 81 other calls in file

ancestors.js

GitHub: elavoie/ssb-tokens

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  })
  console.log(output)
} else if (args.json) {
  pull(
    pull.values(keys),
    pull.asyncMap((msgId,cb) => ssb.get({ id: msgId, meta: true}, cb)),
    pull.collect(function (err, msgs) {
      var output = {}
      msgs.forEach(function (msg) {
        output[msg.key] = msg

+ 236 other calls in file

index.js

GitHub: elavoie/ssb-tokens

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// Get and check all sources
pull(
  pull.values(op.sources),
  pull.asyncMap(get),
  pull.asyncMap((src, cb) => {
    var sId = src.msg.key
    var sOp = src.msg.value.content

    // Valid

+ 839 other calls in file

types.js

GitHub: elavoie/ssb-tokens

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                      Object.keys(types).length + 
                      " results"))

pull(
  pull.values(types),
  pull.asyncMap(function (tok, cb) {
    ssb.about.socialValue(
      { key: 'name', dest: tok.author}, function (err, name) {
        tok.author = { 
          id: tok.author

+ 69 other calls in file

write.js

GitHub: pimterry/it-ws

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pull(
  pull.infinite(function () {
    return 'hello @ ' + Date.now()
  }),
  // throttle so it doesn't go nuts
  pull.asyncMap(function (value, cb) {
    setTimeout(function () {
      cb(null, value)
    }, 100)
  }),

example.js

GitHub: clehner/pull-scroll

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pull.infinite(),
pull.map(function (e) {
  c((c()||0)+1)
  return {random: e, count: c(), top: top}
}),
pull.asyncMap(function (e, cb) {
  var delay = 100 + 200*Math.random()
  setTimeout(function () {
    e.delay = delay
    cb(null, e)

Other functions in pull-stream

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