## isDefined() function

Helper function to narrow a type by excluding undefined/null values.

**Signature:**

```typescript
export declare function isDefined<T>(value: T | undefined | null): value is T;
```

## Parameters

| Parameter | Type                       | Description                     |
| --------- | -------------------------- | ------------------------------- |
| value     | T \| undefined \| null    | The value to refine            |

**Returns:**

value is T

boolean

## Example

```typescript
const arr: Array<number | undefined> = [1,undefined];

const refined: Array<number> = arr.filter(isDefined);
```