Answers for "component did mount"

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how to use componentdidmount in functional component

// passing an empty array as second argument triggers the callback in useEffect
// only after the initial render thus replicating `componentDidMount` lifecycle behaviour
useEffect(() => {
  if(!props.fetched) {
 	 props.fetchRules();
  }
  console.log('mount it!');
}, []);

// componentDidUpdate
useEffect({
	your code here
}) 

// For componentDidUpdate
useEffect(() => {
  // Your code here
}, [yourDependency]);

// For componentWillUnmount
useEffect(() => {
  // componentWillUnmount
  return () => {
     // Your code here
  }
}, [yourDependency]);

Posted by: Guest on June-08-2020

Source

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;

Posted by: Guest on August-28-2020

Source

componentDidUpdate

componentDidUpdate(prevProps, prevState) {
  if (prevState.pokemons !== this.state.pokemons) {
    console.log('pokemons state has changed.')
  }
}

Posted by: Guest on November-10-2020

Source

shouldcomponentupdate

shouldComponentUpdate(nextProps, nextState) {
  return true;
}

Posted by: Guest on June-08-2020

Source

lifecycles if reactjs

class Clock extends React.Component {
  constructor(props) {
    super(props);
    this.state = {date: new Date()};
  }

  componentDidMount() {  }
  componentWillUnmount() {  }
  render() {
    return (
      <div>
        <h1>Hello, world!</h1>
        <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
      </div>
    );
  }
}

Posted by: Guest on July-07-2020

Source

prev props

componentDidUpdate(prevProps) {
  // Utilisation classique (pensez bien à comparer les props) :
  if (this.props.userID !== prevProps.userID) {
    this.fetchData(this.props.userID);
  }
}

Posted by: Guest on June-29-2020

Source

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