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custom hooks in react with two example

more about custom hooks

https://reactjs.org/docs/hooks-custom.html

custom hooks like regular react hooks so you can create your own hooks and make them reusable entities.

one note hook name should start with the use keyword.




working link

https://stackblitz.com/edit/react-wk6ueh


import React, { Component,useEffect,useState } from 'react';
import { render } from 'react-dom';
import Hello from './Hello';
import './style.css';

//usefetchData hook uses to fetch data from any api 
const usefetchData=(url)=>{
  //check status data is loaded or not
  const  [status,setStatus]=useState(false)
  //set data when its loaded sucessfully
  const  [data,setData]=useState(null);
  useEffect(()=>{
    const getData=async()=>{
      const response=await fetch(url).catch((err)=>{
        console.error("Error in fetching")
      });
      const data=await response.json().catch((err)=>{
         console.error("Invaild json type");
      });
      setData(data);
      setStatus(true);
    }
     getData(url);

  },[ ])

  return [status,data];
}
//deep copy
const useDeepCopy=(fromObject)=>{
  const [deepobject,setdeepobject]=useState({});
  const deepCopy=(deepobject,fromObject)=>{
    for(const [key,value] of Object.entries(fromObject))
    {
          if(typeof value==="object")
          {
            let newObject=new Object();
            deepobject[key]=newObject;
            deepCopy(newObject,fromObject[key]);        
          }else
          {
              deepobject[key]=value;
          }
      
    }
  }
  useEffect(()=>{
    
    deepCopy(deepobject,fromObject);
  },[])
  return deepobject;
}
const obj={
    name:"manish",
    age:22,
    working:
    {
      software:"eng",
      lang:"c++,javascript"
    }
  }



//i am dealing with all custom hooks here
const Counter=()=>{
    
  //deep copy of a object and return a newObject
  const newObject=useDeepCopy(obj)
  
  //fetch data from api
  const [status,data]=usefetchData('https://jsonplaceholder.typicode.com/todos/1');
  

  //deep copy custom hook
  useEffect(()=>{
    obj.name="ranjeet";
    obj.working=null;
    console.log("real",obj);
    console.log("copy",newObject)


  },[newObject])
  return <div>
  
   <div>
    {
      //fetch json custom hook
       (!status)?"loading...":"user id=>"+ data.userId+" "+"user data is=>"+data.title
    }</div>
     
  
      </div>
    
   
}
class App extends Component {
  constructor() {
    super();
    this.state = {
      name: 'React'
    };
  }

  render() {
    return (
      <div>
        <Hello name={this.state.name} />
      <Counter/>
      </div>
    );
  }
}

render(<App />, document.getElementById('root'));

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