lodash-a

Asynchronous helpers for lodash.

Early version! Will be adding more methods as needed.

Usage

Install:

npm i lodash-a

Import and use:

const _ = require('lodash');
const _a = require('lodash-a');

_a.pipe(
  fetch,
  _.invoke('json'),
  _.map('author.url'),
  _a.mapParallel(fetch),
  _a.mapParallel(_.invoke('json')),
  _.map('name')
)('https://api.github.com/repos/octocat/Hello-World/commits')
// > ['The Octocat', 'Johnneylee Jack Rollins', 'Spaceghost', ...]

Methods

pipe(fns, data)

awaits each function in sequence, passing the value to each successive function. Equivalent to await fn1(await fn2(await fn3(data))).

Example:

_a.pipe(
  fetch,
  _.invoke('text')
)('https://github.com')
// > The html of github.com

mapParallel(fn, data)

Maps the data using the fn, calling all promises simultaneously and waiting until they all return. Same as Promise.all

Example:

_a.pipe(
  fetch,
  _.invoke('json'),
  _.map('commit.tree.url'),
  _a.mapParallel(fetch),
  _a.mapParallel(_.invoke('json')),
  _.map('sha')
)('https://api.github.com/repos/octocat/Hello-World/commits')
// > The tree sha's of all the commits on the octocat Hello-World repo. All
// requests are fired at once.

mapSequential(fn, data)

Maps the data using the fn, calling all promises sequentially.

Example:

_a.pipe(
  fetch,
  _.invoke('json'),
  _.map('name'),
  _.map(n => `https://api.github.com/repos/octocat/Hello-World/branches/${n}`)
  _a.mapSequential(fetch),
  _a.mapSequential(_.invoke('json')),
  _.map('author.login')
)('https://api.github.com/repos/octocat/Hello-World/branches')
// > The names of all the authors of the branches of the octocate/Hello-World repo, firing off requests sequentially

mapBatches(batchSize, fn, data)

Maps the data using the fn, calling all promise-making functions sequentially in parallel batches of batchSize.

Example:

_a.pipe(
  fetch,
  _.invoke('json'),
  _.map('name'),
  _.map(n => `https://api.github.com/repos/octocat/Hello-World/branches/${n}`)
  _a.mapBatches(5, fetch),
  _a.mapSequential(_.invoke('json')),
  _.map('author.login')
)('https://api.github.com/repos/octocat/Hello-World/branches')
// > The names of all the authors of the branches of the octocate/Hello-World repo, firing off requests in batches of 5

delay(ms, fn, data)

Delays the fn by ms

Example:

_a.pipe(
  fetch,
  _.invoke('json'),
  _.map('name'),
  _.map(n => `https://api.github.com/repos/octocat/Hello-World/branches/${n}`)
  _a.mapBatches(5, _a.delay(1000, fetch)),
  _a.mapSequential(_.invoke('json')),
  _.map('author.login')
)('https://api.github.com/repos/octocat/Hello-World/branches')
// > The names of all the authors of the branches of the octocate/Hello-World repo, firing off requests in batches of 5, delaying each request (effectively, each batch) by 1000 milliseconds

preDelay(ms, fn, data)

Alias for delay

postDelay(ms, fn, data)

Like delay, but delays after the function is called instead of before.

catchWith(catchingFn, fn, data)

Catches the function call with catchingFn.

Example:

_a.pipe([
  _a.catchWith(console.error),
  fetch,
  _.invoke('text')
])('https://google.com')
// > The html of google.com, or undefined, with a logged error, if an error occurred

tap(fn, data)

Calls await fn(data), passing data to the next function and ignoring the return value of fn(data).

Example:

_a.pipe([
  _a.tap(async url => console.log(url)),
  fetch,
  _.invoke('text')
])('https://google.com')
// > The html of google.com, logging the url before fetching

applyValues(object, data)

Accepts an object with functions as each of its properties, calling each of the functions and replacing them with values.

Example:

_a.pipe(
  fetch,
  _.invoke('json'),
  _.map('name'),
  _.map(n => `https://api.github.com/repos/octocat/Hello-World/branches/${n}`)
  _a.mapBatches(5, _a.delay(1000, fetch)),
  _a.mapSequential(_.invoke('json')),
  _a.mapParallel(_a.applyValues({
    commitAuthorName: _.get('commit.commit.author.name'),
    parentCount: _.reduce(_.sum, 0, _.get('commit.parents'))
  }))
)('https://api.github.com/repos/octocat/Hello-World/branches')

[{commitAuthorName: 'The Octocat', parentCount: 2}, ...]