When React first came out, all components were class-based. Developers used this.state to manage the state and this.setState to update it. However, this approach had its challenges: class components often became cumbersome and working with this caused confusion among newcomers.
The release of React 16.8 in 2018 and the introduction by the React team of React Hooks provided a way for managing state and lifecycle in functional components. They have simplified development by cleaning up the code and allowing use of all React features without writing classes.
Why Are the Hooks a Step Forward?
Celadonsoft consider the main advantages of hooks:
- Simplicity — code on hooks is shorter and easier to read than class components.
- Reuse logic — hooks allow you to pass the repeating code into individual functions and reuse them.
- Better code structure — hooks help to separate the logic of components by meaning, not by life cycles.
- Flexibility — hooks allow for easy use of the state and other React capabilities in any component, without being tied to a class architecture.
Basic Hooks: Foundation of Functional Components
React Hooks is a powerful tool, allowing the developer to manage state and component lifecycle without relying on classes. You can verify it by looking at the MVP development here. In this section we will look at the three basic hooks that are most commonly used in React applications: useState, useEffect and useContext.
useState: Managing the State of Functional Components
When we need to store and modify data in the application, for example text in the input field or number of clicks on a button, we can use the useState hook. It allows adding a local state to the functional components, making them dynamic and interactive.
useEffect: Working with Side Effects
Classic React components have used life cycle methods (componentDidMount, componentDidUpdate and componentWillUnmount). In functional components, they are replaced by the hook useEffect. It is needed when the code should be executed after rendering — for example, API requests, event subscriptions or page header changes.
useContext: Convenient Global State
When data has to be transferred across several component nesting levels, the use of props becomes inconvenient. In such cases, useContext helps. It allows you to access the context without passing them manually through props.
Celadonsoft’s hints: These three hooks are the basis of working with state in React hooks. By mastering them, you will be able to create dynamic and effective components, as well as lay the foundation for learning more complex techniques.
Advanced Hooks: Enhancing Capabilities
In the previous section, we have covered basic React hooks that help manage state and side effects. Now let’s dive into more complex hooks that allow you to optimize performance, manage a complex state and interact with DOM elements.
useReducer: Complex State Logic, Alternative to useState
When the state of a component becomes complex, using useState can result in complicated and difficult to manage code. In such cases, useReducer comes to the rescue. This hook works on the principle of managing the state through reducers — a concept familiar to developers working with Redux.
useCallback and useMemo: Performance Optimization
React creates new instances of functions and objects with every reorder, which can lead to unnecessary overrides and decrease in performance. Hook useCallback and useMemo help to avoid this.
- useCallback remembers the function and does not remake it with each reorder, unless the dependency has changed.
- useMemo remembers the result of the calculations and only recalculates it when changing dependencies.
useRef: Access DOM Elements and Save Values
Sometimes you need to work with DOM elements directly, for example, set the focus on input or save a value that does not affect the reender. In such cases, useRef is used.
Hook Rules
Hook is a powerful tool that makes the functional components in React comfortable and flexible. However, their misuse can lead to errors, difficult code debugging and unexpected application behavior. Let’s figure out which rules will help you work effectively with hooks.
1. Hooks can only be called inside components and other hooks
Hooks are designed to work within React components or custom hooks. They cannot be called in normal functions, cycles, conditions or nested blocks of code. This rule is necessary for React to properly track the state and order of hooks.
2. Use hooks only in functional components
Hooks don’t work in the classroom. If you are still writing components on class components, then you should use this.state and componentDidMount to work with the state and effects. But in modern applications, it is recommended to switch to functional components with hooks.
3. Follow the hook call order
React relies on the hook call order inside the component. If you change their order, for example by calling them in conditional constructs or cycles, React will not be able to update the state correctly.
4. Use eslint-plugin-react-hooks to check rules
To avoid errors, the React command recommends using a special ESLint plugin. This plugin automatically checks if the code hooks are used correctly and warns of violations.
Frequently Asked Questions and Common Errors
When learning hooks to React, beginners often face common problems. Break down the most common ones and give recommendations on how to avoid them.
Use of hooks outside the functional component
Hooks only work within functional components or other hooks. If you try to call useState or useEffect outside the component, React will issue an error.
Solution: Make sure that hooks are called only inside the body of the functional component or custom hook.
Skipping dependencies in useEffect
If useEffect uses variables from a component, but they are not specified in the dependency array, it can lead to unexpected bugs.
Solution: Always specify dependencies! And if you need to avoid unnecessary effect calls, consider useCallback or useMemo.
Infinite re-render on change of state
Typically, beginners make a request to the API inside useEffect, but forget about the dependency that changes on each server. This leads to an infinite cycle of updates.
Solution: Check which dependencies are specified in useEffect, and use useRef if the value should not call a re-renderer.
Misuse of useState with objects
Changing the state is not an automatic merging of objects, as in class components.
Solution: If the state is an object, update it through the operator spinner.
Conclusion
The hooks have changed their approach to development on React, making the code cleaner, more understandable and flexible. They allow you to manage the state, work with side effects and organize the reused logic without class components.
