filter() function

f が truthy を返すすべての要素の Iterable/AsyncIterable を返します。

Signature:

declare function filter<A>(
  f: BooleanConstructor,
  iterable: Iterable<A>,
): IterableIterator<TruthyTypesOf<A>>;

Example

const iter = filter((a) => a % 2 === 0, [0, 1, 2, 3, 4, 5, 6]);
iter.next(); // {done:false, value: 0}
iter.next(); // {done:false, value: 2}
iter.next(); // {done:false, value: 4}
iter.next(); // {done:false, value: 6}
iter.next(); // {done:true, value: undefined}

// with pipe
pipe(
  [0, 1, 2, 3, 4, 5, 6],
  filter((a) => a % 2 === 0),
  toArray,
); // [0, 2, 4, 6]

await pipe(
  Promise.resolve([0, 1, 2, 3, 4, 5, 6]),
  filter((a) => a % 2 === 0),
  toArray,
); // [0, 2, 4, 6]

// if you want to use asynchronous callback
await pipe(
  Promise.resolve([0, 1, 2, 3, 4, 5, 6]),
  toAsync,
  filter(async (a) => a % 2 === 0),
  toArray,
); // [0, 2, 4, 6]

// toAsync
await pipe(
  [
    Promise.resolve(0),
    Promise.resolve(1),
    Promise.resolve(2),
    Promise.resolve(3),
    Promise.resolve(4),
    Promise.resolve(5),
    Promise.resolve(6),
  ],
  toAsync,
  filter((a) => a % 2 === 0),
  toArray,
); // [0, 2, 4, 6]

Try It

see pipe, toAsync, toArray

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