metasync

2019-10-09 admin

metasync是什么

什么是metasync,Asynchronous Programming Library

metasync使用教程帮助文档

Asynchronous Programming Library

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Installation

$ npm install metasync

Asynchronous functions composition

metasync(fns)(data, done)

  • fns - array of callback-last functions, callback contranct err-first
  • data - input data (optional)
  • done - err-first callback
  • Returns: composed callback-last / err-first function

composition

const composed = metasync([f1, f2, f3, [[f4, f5, [f6, f7], f8]], f9]);
  • Array of functions gives sequential execution: [f1, f2, f3]
  • Double brackets array of functions gives parallel execution: [[f1, f2, f3]]

Example:

const metasync = require('metasync');
const fs = require('fs');

// Data collector (collect keys by count)
const dc = metasync.collect(4);

dc.pick('user', { name: 'Marcus Aurelius' });
fs.readFile('HISTORY.md', (err, data) => dc.collect('history', err, data));
dc.take('readme', fs.readFile, 'README.md');
setTimeout(() => dc.pick('timer', { date: new Date() }), 1000);

// Key collector (collect certain keys by names)
const kc = metasync
  .collect(['user', 'history', 'readme', 'timer'])
  .timeout(2000)
  .distinct()
  .done((err, data) => console.log(data));

kc.pick('user', { name: 'Marcus Aurelius' });
kc.take('history', fs.readFile, 'HISTORY.md');
kc.take('readme', fs.readFile, 'README.md');
setTimeout(() => kc.pick('timer', { date: new Date() }), 1000);

API

callbackify(fn)

Returns: <Function>

Convert Promise-returning to callback-last / error-first contract

asyncify(fn)

Returns: <Function> with contract: callback-last / error-first

Convert sync function to callback-last / error-first contract

promiseToCallbackLast(promise, callback)

Convert Promise to callback-last

promisify(fn)

Returns: <Function> Promise-returning function

Convert async function to Promise-returning function

promisifySync(fn)

Returns: <Function> Promise-returning function

Convert sync function to Promise object

map(items, fn, done)

Asynchronous map (iterate parallel)

filter(items, fn, done)

Asynchrous filter (iterate parallel)

Example:

metasync.filter(
  ['data', 'to', 'filter'],
  (item, callback) => callback(item.length > 2),
  (err, result) => console.dir(result)
);

reduce(items, fn, done[, initial])

  • items: <Array> incoming
  • fn: <Function> to be executed for each value in array
    • previous: <any> value previously returned in the last iteration
    • current: <any> current element being processed in the array
    • callback: <Function> callback for returning value back to reduce function
    • counter: <number> index of the current element being processed in array
    • items: <Array> the array reduce was called upon
  • done: <Function> on done
  • initial: <any> optional value to be used as first argument in first iteration

Asynchronous reduce

reduceRight(items, fn, done[, initial])

  • items: <Array> incoming
  • fn: <Function> to be executed for each value in array
    • previous: <any> value previously returned in the last iteration
    • current: <any> current element being processed in the array
    • callback: <Function> callback for returning value back to reduce function
    • counter: <number> index of the current element being processed in array
    • items: <Array> the array reduce was called upon
  • done: <Function> on done
  • initial: <any> optional value to be used as first argument in first iteration

Asynchronous reduceRight

each(items, fn, done)

Asynchronous each (iterate in parallel)

Example:

metasync.each(
  ['a', 'b', 'c'],
  (item, callback) => {
    console.dir({ each: item });
    callback();
  },
  (err, data) => console.dir('each done')
);

series(items, fn, done)

Asynchronous series

Example:

metasync.series(
  ['a', 'b', 'c'],
  (item, callback) => {
    console.dir({ series: item });
    callback();
  },
  (err, data) => {
    console.dir('series done');
  }
);

find(items, fn, done)

Asynchronous find (iterate in series)

Example:

metasync.find(
  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16],
  (item, callback) => callback(null, item % 3 === 0 && item % 5 === 0),
  (err, result) => {
    console.dir(result);
  }
);

every(items, fn, done)

Asynchronous every

some(items, fn, done)

Asynchronous some (iterate in series)

asyncMap(items, fn[, options][, done])

Non-blocking synchronous map

asyncIter(base)

Returns: <AsyncIterator>

Create an AsyncIterator instance

class AsyncIterator

AsyncIterator.prototype.constructor(base)

async AsyncIterator.prototype.next()

async AsyncIterator.prototype.count()

async AsyncIterator.prototype.each(fn, thisArg)

async AsyncIterator.prototype.forEach(fn, thisArg)

async AsyncIterator.prototype.parallel(fn, thisArg)

async AsyncIterator.prototype.every(predicate, thisArg)

async AsyncIterator.prototype.find(predicate, thisArg)

async AsyncIterator.prototype.includes(element)

async AsyncIterator.prototype.reduce(reducer, initialValue)

async AsyncIterator.prototype.some(predicate, thisArg)

async AsyncIterator.prototype.someCount(predicate, count, thisArg)

async AsyncIterator.prototype.collectTo(CollectionClass)

async AsyncIterator.prototype.collectWith(obj, collector)

async AsyncIterator.prototype.join(sep = ', ', prefix = ‘’, suffix = ‘’)

async AsyncIterator.prototype.toArray()

AsyncIterator.prototype.map(mapper, thisArg)

AsyncIterator.prototype.filter(predicate, thisArg)

AsyncIterator.prototype.flat(depth = 1)

AsyncIterator.prototype.flatMap(mapper, thisArg)

AsyncIterator.prototype.zip(…iterators)

AsyncIterator.prototype.chain(…iterators)

AsyncIterator.prototype.take(amount)

AsyncIterator.prototype.takeWhile(predicate, thisArg)

AsyncIterator.prototype.skip(amount)

AsyncIterator.prototype.throttle(percent, min)

AsyncIterator.prototype.enumerate()

collect(expected)

Returns: <Collector>

Create Collector instance

class Collector

Data collector

Collector.prototype.constructor(expected)

Data collector

Collector.prototype.collect(key, err, value)

Returns: <this>

Pick or fail key

Collector.prototype.pick(key, value)

Returns: <this>

Pick key

Collector.prototype.fail(key, err)

Returns: <this>

Fail key

Collector.prototype.take(key, fn, args)

Returns: <this>

Take method result

Collector.prototype.timeout(msec)

Returns: <this>

Set timeout

Collector.prototype.done(callback)

Returns: <this>

Set on done listener

Collector.prototype.finalize(key, err, data)

Collector.prototype.distinct(value)

Returns: <this>

Deny or allow unlisted keys

Collector.prototype.cancel(err)

Collector.prototype.then(fulfill, reject)

compose(flow)

Returns: <Function> composed callback-last / err-first

Asynchronous functions composition

Array of functions results in sequential execution: [f1, f2, f3] Double brackets array of functions results in parallel execution: [[f1, f2, f3]]

Example:

const composed = metasync([f1, f2, f3, [[f4, f5, [f6, f7], f8]], f9]);

class Composition

Composition.prototype.constructor()

Composition.prototype.on(name, callback)

Composition.prototype.finalize(err)

Composition.prototype.collect(err, result)

Composition.prototype.parallel()

Composition.prototype.sequential()

Composition.prototype.then(fulfill, reject)

Composition.prototype.clone()

Clone composed

Composition.prototype.pause()

Pause execution

Composition.prototype.resume()

Resume execution

Composition.prototype.timeout(msec)

Set timeout

Composition.prototype.cancel()

Cancel execution where possible

firstOf(fns, callback)

Executes all asynchronous functions and pass first result to callback

parallel(fns[, context], callback)

Parallel execution

Example:

metasync.parallel([f1, f2, f3], (err, data) => {});

sequential(fns[, context], callback)

Sequential execution

Example:

metasync.sequential([f1, f2, f3], (err, data) => {});

runIf(condition[, defaultVal], asyncFn, …args)

  • condition: <any>
  • defaultVal: <any> optional, value that will be returned to callback if condition is falsy.
  • asyncFn: <Function> callback-last function that will be executed if condition if truthy
  • args: <any[]> args to pass to asyncFn

Run asyncFn if condition is truthy, else return defaultVal to callback.

runIfFn(asyncFn, …args)

  • asyncFn: <Function> callback-last function that will be executed if it is provided
  • args: <any[]> args to pass to asyncFn

Run asyncFn if it is provided

class do

do.prototype.constructor(fn, …args)

toAsync(fn)

Returns: <Function>

Convert synchronous function to asynchronous

Transform function with args arguments and callback to function with args as separate values and callback

asAsync(fn, args)

Wrap function adding async chain methods

of(args)

Applicative f => a -> f a

concat(fn1, fn2)

Monoid m => a -> a -> a

fmap(fn1, f)

Functor f => (a -> b) -> f a -> f b

ap(fn, funcA)

Applicative f => f (a -> b) -> f a -> f b

memoize(fn)

Returns: <Function> memoized

Create memoized function

class Memoized

Memoized.prototype.constructor()

Memoized.prototype.clear()

Memoized.prototype.add(key, err, data)

Memoized.prototype.del(key)

Memoized.prototype.get(key, callback)

Memoized.prototype.on(eventName, listener)

Add event listener

Example:

const memoized = new Memoized();
memoized.on('memoize', (err, data) => { ... });
memoized.on('add', (key, err, data) => { ... });
memoized.on('del', (key) => { ... })
memoized.on('clear', () => { ... });

Memoized.prototype.emit(eventName, args)

  • eventName: <string>
  • args: <any> rest arguments

Emit Memoized events

poolify(factory, min, norm, max)

queue(concurrency)

  • concurrency: <number> simultaneous and asynchronously executing tasks

Returns: <Queue>

Create Queue instance

class Queue

Queue constructor

Queue.prototype.constructor(concurrency)

  • concurrency: <number> asynchronous concurrency

Queue constructor

Queue.prototype.wait(msec)

  • msec: <number> wait timeout for single item

Returns: <this>

Set wait before processing timeout

Queue.prototype.throttle(count[, interval])

  • count: <number> item count
  • interval: <number> per interval, optional default: 1000 msec

Returns: <this>

Throttle to limit throughput

Queue.prototype.add(item[, factor[, priority]])

Returns: <this>

Add item to queue

Queue.prototype.next(task)

  • task: <Array> next task [item, factor, priority]

Returns: <this>

Process next item

Queue.prototype.takeNext()

Returns: <this>

Prepare next item for processing

Queue.prototype.pause()

Returns: <this>

Pause queue

This function is not completely implemented yet

Queue.prototype.resume()

Returns: <this>

Resume queue

This function is not completely implemented yet

Queue.prototype.clear()

Returns: <this>

Clear queue

Queue.prototype.timeout(msec, onTimeout)

Returns: <this>

Set timeout interval and listener

Queue.prototype.process(fn)

Returns: <this>

Set processing function

Queue.prototype.done(fn)

Returns: <this>

Set listener on processing done

Queue.prototype.success(listener)

Returns: <this>

Set listener on processing success

Queue.prototype.failure(listener)

Returns: <this>

Set listener on processing error

Queue.prototype.drain(listener)

Returns: <this>

Set listener on drain Queue

Queue.prototype.fifo()

Returns: <this>

Switch to FIFO mode (default for Queue)

Queue.prototype.lifo()

Returns: <this>

Switch to LIFO mode

Queue.prototype.priority(flag)

  • flag: <boolean> default: true, false will disable priority mode

Returns: <this>

Activate or deactivate priority mode

Queue.prototype.roundRobin(flag)

  • flag: <boolean> default: true, false will disable roundRobin mode

Returns: <this>

Activate or deactivate round robin mode

Queue.prototype.pipe(dest)

  • dest: <Queue> destination queue

Returns: <this>

Pipe processed items to different queue

throttle(timeout, fn, …args)

Returns: <Function>

Get throttling function, executed once per interval

debounce(timeout, fn, …args)

Debounce function, delayed execution

timeout(timeout, fn, callback)

Set timeout for asynchronous function execution

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