part 5 - usecontext 1

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app.js
import React, { useState, useEffect } from 'react';
import './App.css'
import ComponentC from './ComponentE';
export const UserContext = React.createContext()
export const SalaryContext = React.createContext()

const App = () => {

  return (
    <div className="App">
      <UserContext.Provider value={'john doe'}>
        <SalaryContext.Provider value={"12345"}>
          <ComponentE />
        </SalaryContext.Provider>
      </UserContext.Provider>

    </div>
  );
}

export default App;
//useEffect runs after every render of component

ComponentF.js
import React, { useContext } from 'react'

import { UserContext, SalaryContext } from './App'

function ComponentF() {
    console.log("C F")
    const user = useContext(UserContext)
    const salary = useContext(SalaryContext)
    return (
        <div>
            {user} has salary {salary}
        </div>
    )
}

export default ComponentF

ComponentE.js

import React from 'react'
import ComponentF from './ComponentF';
function ComponentE() {
    console.log("C E")
    return (
        <div>
            <ComponentF />
        </div>
    )
}

export default ComponentE

Comments

part 2 react hooks with objects and array

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react hooks part 1

. import React , { useState } from 'react' ; import './App.css' const App = () => { const [ count1 , setCount1 ] = useState ( 1 ) const [ count2 , setCount2 ] = useState ( 2 ) const [{ count3 , count4 }, setCount ] = useState ({ count3 : 8 , count4 : 9 }) return ( <div className = "App" > <button onClick = { () => { setCount1 ( c => c + 1 ) setCount2 ( c => c + 1 ) } } > Add-it </button> <div> count1= { count1 } </div> <div> count2= { count2 } </div> <button onClick = { () => { setCount (( c ) => ({ ... c , count3 : count3 + 100 , count4 : count4 + 100 }) ) //here "c" is currentstate and the ...c spreadoperator } } > add obj </button> <div> count3= { count3 } </div><div> count4= { count4 } </div> </div> ); } export def...

part 4, fetch data with useEffect axios

-------------------------------------------------------------------------- import React , { useState , useEffect } from 'react' ; import axios from 'axios' const DataPull = () => { const [ id , setId ] = useState ( 1 ) const [ post , setPost ] = useState ({}) const [ buttonid , setButtonid ] = useState ( 1 ) const handleClick = () => { console . log ( "button id set" ) setButtonid ( id ) } useEffect (() => { console . log ( "normal id " + id ) console . log ( "button id " + buttonid ) axios . get ( `https://jsonplaceholder.typicode.com/posts/ ${ buttonid } ` ). then ( res => { setPost ( res . data ) }). catch ( err => { console . log ( err ) setPost ({ title : "no data" }) }) }, [ buttonid ]) return ( <div> <input type = "text" ...

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