In this chapter, we will learn how to use events in ReactJS.
Simple Example
This is a simple example where we will only use one component. We are just adding onClick event that will trigger updateState function once the button is clicked.
App.jsx
import React from 'react';
class App extends React.Component {
constructor(props) {
super(props);
this.state = {
data: 'Initial data...'
}
this.updateState = this.updateState.bind(this);
};
updateState() {
this.setState({data: 'Data updated...'})
}
render() {
return (
<div>
<button onClick = {this.updateState}>CLICK</button>
<h4>{this.state.data}</h4>
</div>
);
}
}
export default App;
main.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App.jsx';
ReactDOM.render(<App/>, document.getElementById('app'));
This will produce the following result.
Child Events
When we need to update the state of the parent component from its child, we can create an event handler (updateState) in the parent component and pass it as a prop (updateStateProp) to the child component where we can just call it.
App.jsx
import React from 'react';
class App extends React.Component {
constructor(props) {
super(props);
this.state = {
data: 'Initial data...'
}
this.updateState = this.updateState.bind(this);
};
updateState() {
this.setState({data: 'Data updated from the child component...'})
}
render() {
return (
<div>
<Content myDataProp = {this.state.data}
updateStateProp = {this.updateState}></Content>
</div>
);
}
}
class Content extends React.Component {
render() {
return (
<div>
<button onClick = {this.props.updateStateProp}>CLICK</button>
<h3>{this.props.myDataProp}</h3>
</div>
);
}
}
export default App;
main.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App.jsx';
ReactDOM.render(<App/>, document.getElementById('app'));
This will produce the following result.
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