1---
2category: Utilities
3---
4 
5# isDefined
6 
7Non-nullish checking type guard for Ref.
8 
9## Usage
10 
11```ts
12import { isDefined } from '@vueuse/core'
13 
14const example = ref(Math.random() ? 'example' : undefined) // Ref<string | undefined>
15 
16if (isDefined(example))
17  example // Ref<string>
18```
19 
20## Type Declarations
21 
22```ts
23export type IsDefinedReturn = boolean
24export declare function isDefined<T>(
25  v: ComputedRef<T>,
26): v is ComputedRef<Exclude<T, null | undefined>>
27export declare function isDefined<T>(
28  v: Ref<T>,
29): v is Ref<Exclude<T, null | undefined>>
30export declare function isDefined<T>(v: T): v is Exclude<T, null | undefined>
31```
32