1---
2category: '@Math'
3related: createGenericProjection
4---
5 
6# useProjection
7 
8Reactive numeric projection from one domain to another.
9 
10## Usage
11 
12```ts
13import { useProjection } from '@vueuse/math'
14 
15const input = ref(0)
16const projected = useProjection(input, [0, 10], [0, 100])
17 
18input.value = 5 // projected.value === 50
19input.value = 10 // projected.value === 100
20```
21 
22## Type Declarations
23 
24```ts
25/**
26 * Reactive numeric projection from one domain to another.
27 *
28 * @see https://vueuse.org/useProjection
29 *
30 * @__NO_SIDE_EFFECTS__
31 */
32export declare function useProjection(
33  input: MaybeRefOrGetter<number>,
34  fromDomain: MaybeRefOrGetter<readonly [number, number]>,
35  toDomain: MaybeRefOrGetter<readonly [number, number]>,
36  projector?: ProjectorFunction<number, number>,
37): ComputedRef<number>
38```
39