React State The state is an updatable structure. In a component, change in state over time can happen. The state is used to contain data or information about the component and also take the responsibility to make a component dynamic and interactive. The components that have their own state are known as a stateful component, while the components that don’t have their own state are known as a stateless component.
Methods: setState() method: It is used to set a state and it also triggers UI updates on calling. getInitialState(): It is used to set an initial state before any interaction occurs.
Defining State Example:
import React, { Component } from 'react';
class App extends React.Component {
constructor() {
super();
this.state = {
data:
[ {
"name":"Dhoni"
},
{
"name":"Kohli"
},
{
"name":"Pandya"
} ]
}
}
render() {
return (
{this.state.data.map((item) =>
)}
);
}
}
class PLAYERname extends React.Component {
render() {
return (
Player Names
);
}
}
class List extends React.Component {
render() {
return (
- {this.props.data.name}
Output:
Player Names
● Dhoni
● Kohli
● Pandya
Explanation: To declare a default set of values a class constructor is used. It assigns an initial state using this.state. The render() method renders the ‘this.state’ property. Here we are creating a stateful component using ES6 syntax. The super() method initializes this.state.
Changing the State: We can also change the component state. For this, we are using the setState() method. We then pass a new state object as the argument.
Example:
import React, { Component } from 'react';
class App extends React.Component {
constructor() {
super();
this.state = { displayBio: false };
console.log('Component this', this);
this.toggleDisplayBio = this.toggleDisplayBio.bind(this);
}
toggleDisplayBio(){
this.setState({displayBio: !this.state.displayBio});
}
render() {
return (
Hello World
{
this.state.displayBio ? (
Have a Great Day.
) : (
)}
)
}
}
export default App;
Output 1: 
