1---
2category: Array
3---
4 
5# useArrayReduce
6 
7Reactive `Array.reduce`.
8 
9## Usage
10 
11```ts
12import { useArrayReduce } from '@vueuse/core'
13 
14const sum = useArrayReduce([ref(1), ref(2), ref(3)], (sum, val) => sum + val)
15// sum.value: 6
16```
17 
18### Use with reactive array
19 
20```ts
21import { useArrayReduce } from '@vueuse/core'
22 
23const list = reactive([1, 2])
24const sum = useArrayReduce(list, (sum, val) => sum + val)
25 
26list.push(3)
27// sum.value: 6
28```
29 
30### Use with initialValue
31 
32```ts
33import { useArrayReduce } from '@vueuse/core'
34 
35const list = reactive([{ num: 1 }, { num: 2 }])
36const sum = useArrayReduce(list, (sum, val) => sum + val.num, 0)
37// sum.value: 3
38```
39 
40## Type Declarations
41 
42```ts
43export type UseArrayReducer<PV, CV, R> = (
44  previousValue: PV,
45  currentValue: CV,
46  currentIndex: number,
47) => R
48export type UseArrayReduceReturn<T = any> = ComputedRef<T>
49/**
50 * Reactive `Array.reduce`
51 *
52 * @see https://vueuse.org/useArrayReduce
53 * @param list - the array was called upon.
54 * @param reducer - a "reducer" function.
55 *
56 * @returns the value that results from running the "reducer" callback function to completion over the entire array.
57 *
58 * @__NO_SIDE_EFFECTS__
59 */
60export declare function useArrayReduce<T>(
61  list: MaybeRefOrGetter<MaybeRefOrGetter<T>[]>,
62  reducer: UseArrayReducer<T, T, T>,
63): UseArrayReduceReturn<T>
64/**
65 * Reactive `Array.reduce`
66 *
67 * @see https://vueuse.org/useArrayReduce
68 * @param list - the array was called upon.
69 * @param reducer - a "reducer" function.
70 * @param initialValue - a value to be initialized the first time when the callback is called.
71 *
72 * @returns the value that results from running the "reducer" callback function to completion over the entire array.
73 *
74 * @__NO_SIDE_EFFECTS__
75 */
76export declare function useArrayReduce<T, U>(
77  list: MaybeRefOrGetter<MaybeRefOrGetter<T>[]>,
78  reducer: UseArrayReducer<U, T, U>,
79  initialValue: MaybeRefOrGetter<U>,
80): UseArrayReduceReturn<U>
81```
82