---
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://docs.rs/yew/0.20.0/yew/functional/index.html)

### 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.
