async-array

AsyncArray is a class that inheriths from Array and adds async methods with support for async callbacks such as asyncForEach, asyncMap etc:

const existing = await AsyncArray.of(1, 2, 3)
    .asyncFilter(async (id) => existsInDatabase(id))

Installation

npm install @ziggy42/async-array

Usage

The constructor of AsyncArray behaves exactly like Array. From MDN:

A JavaScript array is initialized with the given elements, except in the case where a single argument is passed to the Array constructor and that argument is a number.
If the only argument passed to the Array constructor is an integer between 0 and 232-1 (inclusive), this returns a new JavaScript array with its length property set to that number (Note: this implies an array of arrayLength empty slots, not slots with actual undefined values). If the argument is any other number, a RangeError exception is thrown.

const arr1 = new AsyncArray(1, 2, 3) // AsyncArray [ 1, 2, 3 ]

const arr2 = new AsyncArray(3) // AsyncArray [ <3 empty items> ]

There are also two static functions to create new AsyncArray instances:

const arr1 = AsyncArray.of(1, 2, 3) // AsyncArray [ 1, 2, 3 ]

const arr2 = AsyncArray.from([1, 2, 3]) // AsyncArray [ 1, 2, 3 ]

A regular Array can be obtained form an AsyncArray:

const arr = AsyncArray.of(1, 2, 3).toArray() // [ 1, 2, 3 ]

AsyncArray adds the following methods:

• asyncEvery
• asyncFilter
• asyncFind
• asyncFindIndex
• asyncFlatMap
• asyncForEach
• asyncMap
• asyncReduce
• asyncReduceRight
• asyncSome

These methods behave exactly like the non-async versions but they accept async callbacks.

const existing = await AsyncArray.of('1', '2', '3')
    .asyncFilter(async (id) => existsInDatabase(id))

Be aware that the async callbacks are executed in sequence, NOT in parallel. The following methods allow you to execute the callbacks in parallel instead:

• asyncFilterAll
• asyncMapAll

const existing = await AsyncArray.of(1, 2, 3)
    .asyncFilterAll(async (id) => existsInDatabase(id))