rc-js-util/docs/rc-js-util.arrayindex.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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## arrayIndex() function

Populates a `Map` given a key creating function and `ArrayLike`<!-- -->.

**Signature:**

```typescript
export declare function arrayIndex<TKey, TItem>(items: ArrayLike<TItem>, getKey: (item: TItem, index: number) => TKey | null): Map<Exclude<TKey, null>, TItem>;
```

## Parameters

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

Parameter


</th><th>

Type


</th><th>

Description


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

items


</td><td>

ArrayLike&lt;TItem&gt;


</td><td>


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

getKey


</td><td>

(item: TItem, index: number) =&gt; TKey \| null


</td><td>


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

Map&lt;Exclude&lt;TKey, null&gt;, TItem&gt;

## Remarks

keys which are null are omitted.

See [arrayIndex()](./rc-js-util.arrayindex.md)<!-- -->.