How re-render a component without using setState() method in ReactJS ?
In React, to re-render a class-based component with an updated state we generally use the setState() method. But instead, we can use other methods to re-render a component without using setState().
Prerequisites:
Approaches to re-render a component without using setState() method are.
Table of Content
Steps to Create React Application:
Step 1: Create a React application using the following command:
npx create-react-app foldername
Step 2: After creating your project folder i.e. foldername, move to it using the following command:
cd foldername
Project Structure:
Method 1: by changing props
If we pass the state of the parent component as a prop to the child and call setState on the parent, it will cause the re-render of the child component as its props are changed.
Example: This code implements re-render by changing the props passed to the component.
Javascript
// Filename - App.jsimport React, { Component } from "react";class App extends Component { constructor(props) { super(props); // Set initial state of parent this.state = { category: "Coder" }; // Binding this keyword this.updateState = this.updateState.bind(this); } updateState() { // Changing state this.setState({ category: "Geek" }); } render() { return ( <div> <Child category={this.state.category} /> <button onClick={this.updateState}> Click me! </button> </div> ); }}class Child extends Component { render() { return ( <div> <p>Hi {this.props.category}!</p> </div> ); }}export default App; |
Step to Run Application: Run the application using the following command from the root directory of the project:
npm start
Output: Now open your browser and go to http://localhost:3000/, you will see the following output:
re-render of child component by changing props
Method 2: Using the forceUpdate() method
The forceUpdate method forcible re-render the component. When forceUpdate is called it directly calls the render method by skiping other lifecycle methods and update the interface.
Caution: Even though forceUpdate solves our problem but it is advised to use setState or changing props to re-render a component as forceUpdate method skips the proper lifecycle of rendering of a component. See this for detail.
Example: This example implements re-render forcibly using the forceUpdate method.
Javascript
// Filename - App.jsimport React, { Component } from "react";class App extends Component { reRender = () => { // force update this.forceUpdate(); }; render() { return ( <div> <h2>Random Number Generator</h2> <p> Your Number:{" "} {Math.floor(Math.random() * 10) + 1} </p> <button onClick={this.reRender}> Generate! </button> </div> ); }}export default App; |
Step to Run Application: Run the application using the following command from the root directory of the project:
npm start
Output: Now open your browser and go to http://localhost:3000/, you will see the following output:
generate a random number by forceUpdate method
