---title: 'proxyWithComputed'section: 'API'subSection: 'Utils'description: ''---
# proxyWithComputed
#### add a computation to a proxy
You can define own computed properties within a proxy.By combining with a memoization library such as[proxy-memoize](https://github.com/dai-shi/proxy-memoize),optimizing function calls is possible.
Be careful not to overuse `proxy-memoize`because `proxy-memoize` and `useSnapshot` do similar optimizationand double optimization may lead to less performance.
```jsimport memoize from 'proxy-memoize'import { proxyWithComputed } from 'valtio/utils'
const state = proxyWithComputed( { count: 1, }, { doubled: memoize((snap) => snap.count * 2), })
// Computed values accept custom setters too:const state2 = proxyWithComputed( { firstName: 'Alec', lastName: 'Baldwin', }, { fullName: { get: memoize((snap) => snap.firstName + ' ' + snap.lastName), set: (state, newValue) => { ;[state.firstName, state.lastName] = newValue.split(' ') }, }, })
// if you want a computed value to derive from another computed, you must declare the dependency first:const state = proxyWithComputed( { count: 1, }, { doubled: memoize((snap) => snap.count * 2), quadrupled: memoize((snap) => snap.doubled * 2), })```
The last use case fails to infer types in TypeScript[#192](https://github.com/pmndrs/valtio/issues/192).