Muhammad Hamza 12c9ebb0ea
Move hook API docs to Rustdoc (#2628)
* Move hook API docs to Rustdoc

* npm update, fix links and doc tests and callback docs

* make doc tests pass

* Update packages/yew/src/functional/hooks/use_ref.rs

* Update packages/yew/src/functional/hooks/use_ref.rs

* Update use_ref.rs
2022-04-21 15:28:09 +05:00

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---
title: 'Hooks'
slug: /concepts/function-components/hooks
---
## Hooks
Hooks are functions that let you store state and perform side-effects.
Yew comes with a few pre-defined Hooks. You can also create your own or discover many [community made hooks](/community/awesome#hooks).
## Rules of hooks
1. A hook function name always has to start with `use_`
2. Hooks can only be used in the following locations:
- Top level of a function / hook.
- Blocks inside a function / hook, given it's not already branched.
- In the condition of a top level `if` expression inside a function / hook.
- In the scrutinee of a top level `match` expression inside a function / hook.
3. Hooks must be called in the same order for every render. Returning early is only allowed when using [Suspense](../../suspense.mdx)
These rules are enforced by either compile time or run-time errors.
### Pre-defined Hooks
Yew comes with the following predefined Hooks:
- `use_state`
- `use_state_eq`
- `use_memo`
- `use_callback`
- `use_mut_ref`
- `use_node_ref`
- `use_reducer`
- `use_reducer_eq`
- `use_effect`
- `use_effect_with_deps`
- `use_context`
- `use_force_update`
The documentation for these hooks can be found in the [Yew API docs](https://yew-rs-api.web.app/next/yew/functional/)
### Custom Hooks
There are cases where you want to define your own Hooks to encapsulate potentially stateful logic from a component into reusable functions.
See the [Defining custom hooks](concepts/function-components/hooks/custom-hooks.mdx#defining-custom-hooks) section for more information.
## Further reading
- The React documentation has a section on [React hooks](https://reactjs.org/docs/hooks-intro.html).
These are not exactly the same as Yew's hooks, but the underlying concept is similar.