JS Practice — Built-in Objects

Array.fromAsync() — map each element

📖 Usage Example

const nums = [1, 2, 3]
const doubled = await Array.fromAsync(nums, async n => n * 2)
// → [2, 4, 6]

Pass an async mapping function to Array.fromAsync() to transform each element as it resolves.

Array.fromAsync() — with a mapping function

Like Array.from(), Array.fromAsync() accepts an optional mapping function as its second argument. The mapper can itself be async (returning a promise).

This exercise simulates the pattern synchronously.

Challenge: Implement doubleAll that doubles every number in an array using Array.from with a mapping function.

doubleAll([1, 2, 3]) // → [2, 4, 6]

💡 Hints (2)

• `Array.from(iterable, mapFn)` applies `mapFn` to each element during construction.
• The async version `Array.fromAsync(iterable, async x => ...)` awaits each mapped value.