# mapAsync

Creates a map schema.

```ts
const Schema = v.mapAsync<TKey, TValue, TMessage>(key, value, message);
```

## Generics

- `TKey` <Property {...properties.TKey} />
- `TValue` <Property {...properties.TValue} />
- `TMessage` <Property {...properties.TMessage} />

## Parameters

- `key` <Property {...properties.key} />
- `value` <Property {...properties.value} />
- `message` <Property {...properties.message} />

### Explanation

With `mapAsync` you can validate the data type of the input and whether the entries match `key` and `value`. If the input is not a map, you can use `message` to customize the error message.

## Returns

- `Schema` <Property {...properties.Schema} />

## Examples

The following examples show how `mapAsync` can be used.

### Shopping items schema

Schema to validate a map with usernames that are allowed to shop as keys and the total items purchased as values.

```ts
import { isUserVerified } from '~/api';

const ShoppingItemsSchema = v.mapAsync(
  v.pipeAsync(
    v.string(),
    v.checkAsync(isUserVerified, 'The username is not allowed to shop.')
  ),
  v.pipe(v.number(), v.minValue(0))
);
```

## Related

The following APIs can be combined with `mapAsync`.

### Schemas

<ApiList
  items={[
    'any',
    'array',
    'bigint',
    'blob',
    'boolean',
    'custom',
    'date',
    'enum',
    'exactOptional',
    'file',
    'function',
    'instance',
    'intersect',
    'lazy',
    'literal',
    'looseObject',
    'looseTuple',
    'nan',
    'never',
    'nonNullable',
    'nonNullish',
    'nonOptional',
    'null',
    'nullable',
    'nullish',
    'number',
    'object',
    'objectWithRest',
    'optional',
    'picklist',
    'promise',
    'record',
    'set',
    'strictObject',
    'strictTuple',
    'string',
    'symbol',
    'tuple',
    'tupleWithRest',
    'undefined',
    'undefinedable',
    'union',
    'unknown',
    'variant',
    'void',
  ]}
/>

### Methods

<ApiList items={['config', 'getDefault', 'getFallback']} />

### Actions

<ApiList
  items={[
    'check',
    'brand',
    'description',
    'flavor',
    'guard',
    'maxSize',
    'metadata',
    'minSize',
    'notSize',
    'rawCheck',
    'rawTransform',
    'readonly',
    'size',
    'title',
    'transform',
  ]}
/>

### Utils

<ApiList items={['entriesFromList', 'isOfKind', 'isOfType']} />

### Async

<ApiList
  items={[
    'arrayAsync',
    'checkAsync',
    'customAsync',
    'exactOptionalAsync',
    'fallbackAsync',
    'getDefaultsAsync',
    'getFallbacksAsync',
    'intersectAsync',
    'lazyAsync',
    'looseObjectAsync',
    'looseTupleAsync',
    'nonNullableAsync',
    'nonNullishAsync',
    'nonOptionalAsync',
    'nullableAsync',
    'nullishAsync',
    'objectAsync',
    'objectWithRestAsync',
    'optionalAsync',
    'parseAsync',
    'parserAsync',
    'pipeAsync',
    'rawCheckAsync',
    'rawTransformAsync',
    'recordAsync',
    'safeParseAsync',
    'safeParserAsync',
    'setAsync',
    'strictObjectAsync',
    'strictTupleAsync',
    'transformAsync',
    'tupleAsync',
    'tupleWithRestAsync',
    'unionAsync',
    'variantAsync',
  ]}
/>