componenet will unmount code example

Example 1: react native class component constructor

import React from 'react';  
import { View, TextInput } from "react-native";

class App extends React.Component {  
  constructor(props){  
    super(props);  
    this.state = {  
         name: "" 
      }  
    this.handleChange = this.handleChange.bind(this);  
  }
  handleChange(text){
    this.setState({ name: text })
    console.log(this.props);  
  }  
  render() {  
    return (  
    <View>
      <TextInput 
      	value={this.state.name} 
  		onChangeText={(text) =>this.handleChange(text)}
      />
    </View>  
  }  
}  
export default App;

Example 2: set state

class App extends React.Component {

state = { count: 0 }

handleIncrement = () => {
  this.setState({ count: this.state.count + 1 })
}

handleDecrement = () => {
  this.setState({ count: this.state.count - 1 })
}
  render() {
    return (
      <div>
        <div>
          {this.state.count}
        </div>
        <button onClick={this.handleIncrement}>Increment by 1</button>
        <button onClick={this.handleDecrement}>Decrement by 1</button>
      </div>
    )
  }
}