rc-js-util/docs/rc-js-util.mapunion.md

A collection of TS and C++ utilities to help writing performant and correct applications, achieved through strict typing and (removable) invariant checking.

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## mapUnion() function

Returns a map with keys from both A and B. If both A and B have the same key the value from B will be used.

**Signature:**

```typescript
export declare function mapUnion<TKey, TIem>(a: ReadonlyMap<TKey, TIem>, b: ReadonlyMap<TKey, TIem>): Map<TKey, TIem>;
```

## Parameters

<table><thead><tr><th>

Parameter


</th><th>

Type


</th><th>

Description


</th></tr></thead>
<tbody><tr><td>

a


</td><td>

ReadonlyMap&lt;TKey, TIem&gt;


</td><td>


</td></tr>
<tr><td>

b


</td><td>

ReadonlyMap&lt;TKey, TIem&gt;


</td><td>


</td></tr>
</tbody></table>
**Returns:**

Map&lt;TKey, TIem&gt;

## Remarks

See [mapUnion()](./rc-js-util.mapunion.md)<!-- -->.