Understanding ReactJS Lifecycle
Tags: javascript, react, learning, webdev
Published: 2023-05-02 14:35:44

ReactJS, a popular front-end library, is known for its efficient rendering of user interfaces. One of the key features of ReactJS is its lifecycle methods. The lifecycle methods provide a way for developers to manage components and their behavior throughout their lifecycle. In this article, we will dive deep into the ReactJS lifecycle and understand how it works.
What is ReactJS Lifecycle?

ReactJS components have a lifecycle which consists of different stages. The lifecycle methods are functions that get called at different stages of a component's lifecycle. The lifecycle can be divided into three main phases: Mounting, Updating, and Unmounting.

### Mounting
Mounting is the first phase of the ReactJS lifecycle. In this phase, the component is created and added to the DOM. There are four methods in this phase:

### constructor()
This method is called when the component is created. It is used to initialize the component's state and bind event handlers.

### getDerivedStateFromProps()
This method is called after the constructor and before the render method. It is used to update the component's state based on changes in its props.

### render()
This method is called after getDerivedStateFromProps(). It returns the JSX that defines the component's structure.

### componentDidMount()
This method is called after the component is added to the DOM. It is used to perform any initialization that requires access to the DOM.

### Updating
The updating phase is the second phase of the ReactJS lifecycle. In this phase, the component's props or state changes and the component is re-rendered. There are five methods in this phase:

### getDerivedStateFromProps()
This method is called again when the component's props change. It is used to update the component's state based on changes in its props.

### shouldComponentUpdate()
This method is called before the component is re-rendered. It is used to determine whether the component should be re-rendered or not.

### render()
This method is called after shouldComponentUpdate() and returns the updated JSX.

### getSnapshotBeforeUpdate()
This method is called before the updated JSX is added to the DOM. It is used to capture the current state of the component.

### componentDidUpdate()
This method is called after the updated JSX is added to the DOM. It is used to perform any post-rendering operations.

### Unmounting
The unmounting phase is the last phase of the ReactJS lifecycle. In this phase, the component is removed from the DOM. There is only one method in this phase:

### componentWillUnmount()
This method is called before the component is removed from the DOM. It is used to perform any cleanup operations.

### Conclusion
ReactJS lifecycle methods provide a way for developers to manage components and their behavior throughout their lifecycle. Understanding the ReactJS lifecycle is essential for writing efficient and optimized code. By using the lifecycle methods, developers can control the behavior of their components and improve the performance of their applications.

In this article, we covered the three phases of the ReactJS lifecycle: Mounting, Updating, and Unmounting. We also discussed the methods that are called in each phase and their importance. With this knowledge, you can write better ReactJS components and create better user interfaces.