API reference › @evolu/common › Array › flatMapArray

Call Signature

function flatMapArray<T>(
  array:
    | readonly [readonly [T, T] | [T, ...T[]], readonly [T, T] | [T, ...T[]]]
    | [readonly [T, T] | [T, ...T[]], ...(readonly [T, T] | [T, ...T[]])[]],
): readonly [T, T];

Defined in: packages/common/src/Array.ts:363

Maps each element to an array and flattens the result.

Preserves non-empty type when the input is non-empty and the mapper returns non-empty arrays. When called without a mapper, flattens nested arrays using identity.

Example

flatMapArray([
  [1, 2],
  [3, 4],
]); // [1, 2, 3, 4]

flatMapArray([1, 2, 3], (x) => [x, x * 10]); // [1, 10, 2, 20, 3, 30]

Filter and map in one pass

Return [] to filter out, [value] to keep:

const errors = flatMapArray(fields, (f) => {
  const result = validate(f);
  return result.ok ? [] : [result.error];
});

Call Signature

function flatMapArray<T>(
  array: readonly (readonly T[] | T[])[] | (readonly T[] | T[])[],
): readonly T[];

Defined in: packages/common/src/Array.ts:369

Possibly empty nested arrays.

Call Signature

function flatMapArray<T, U>(
  array: readonly [T, T] | [T, ...T[]],
  mapper: (item: T, index: number) => readonly [U, U] | [U, ...U[]],
): readonly [U, U];

Defined in: packages/common/src/Array.ts:375

Non-empty with mapper returning non-empty.

Call Signature

function flatMapArray<T, U>(
  array: readonly T[] | T[],
  mapper: (item: T, index: number) => readonly U[] | U[],
): readonly U[];

Defined in: packages/common/src/Array.ts:383

With mapper function.

Markdown for LLMs