Lifecycle and Hooks

How is lifecycle method and hooks similar and different?

React lifecycle methods and hooks both allow you to tap into different phases of a component’s lifecycle, such as when it is first added to the DOM, when it updates, and when it is removed from the DOM.

However, they differ in how they’re used and in what kind of components they can be used.

Lifecycle Methods:

Lifecycle methods are used in class components. They are special methods that automatically get called during different stages of a component’s lifecycle. The key lifecycle methods are:

  • componentDidMount: Called once the component has been rendered to the DOM.
  • componentDidUpdate: Called whenever the component is updated (i.e., state or props change).
  • componentWillUnmount: Called just before the component is unmounted and destroyed.

Hooks:

React hooks, introduced in React 16.8, allow you to use state and other React features in functional components. The key hooks related to lifecycle methods are:

  • useState: Allows you to add state to functional components.
  • useEffect: Lets you perform side effects in functional components. It can be considered equivalent to componentDidMount, componentDidUpdate, and componentWillUnmount combined.
  • useContext: Allows you to use React context for sharing state down the component tree.

Similarities:

Both lifecycle methods and hooks:

  • Allow you to run code at specific points in a component’s lifecycle.
  • Enable side effects like fetching data, manual DOM manipulation, setting up subscriptions, etc.

Differences:

  • Lifecycle methods are used in class components, whereas hooks are used in functional components.
  • Hooks provide a simpler syntax and reduce the amount of code you need to write compared to lifecycle methods. They also avoid some of the complexities and pitfalls of classes.
  • Hooks enable you to use state and other React features without writing a class, making code more readable and easier to test.
  • Lifecycle methods can sometimes cause confusion because they can be invoked at different points in a component’s lifecycle and it’s not always clear when they will be invoked. useEffect, on the other hand, unifies these lifecycles into a single API.
  • useEffect hooks can be thought of as being “component lifecycle aware”, meaning you can control whether they run on mount, update, or unmount by passing an array of dependencies as the second argument.

The React team recommends using hooks for new component development. However, lifecycle methods in class components are still widely used in existing codebases, so it’s important to understand both.