add an object to array in react hooks useState code example

Example 1: How to add object in an array using useState

import React, { useState } from 'react';
 
function App() {
 
  const [items, setItems] = useState([]);
 
  // handle click event of the button to add item
  const addMoreItem = () => {
    setItems(prevItems => [...prevItems, {
      id: prevItems.length,
      value: getRandomNumber()
    }]);
  }
 
  // generate 6 digit random number
  const getRandomNumber = () => {
    return Math.random().toString().substring(2, 8);
  }
 
  return (
    

      
useState with an array in React Hooks - Clue Mediator
      

      Add More
      


      Output:
      
{JSON.stringify(items, null, 2)}
    
  );
}
 
export default App;

Example 2: react setstate in hooks to array of objects value

// sample datas structure
/* const datas = [
    {
      id:   1,
      name: 'john',
      gender: 'm'
    }
    {
      id:   2,
      name: 'mary',
      gender: 'f'
    }
] */ // make sure to set the default value in the useState call (I already fixed it)

const [datas, setDatas] = useState([
    {
      id:   1,
      name: 'john',
      gender: 'm'
    }
    {
      id:   2,
      name: 'mary',
      gender: 'f'
    }
]);

const updateFieldChanged = index => e => {

    console.log('index: ' + index);
    console.log('property name: '+ e.target.name);
    let newArr = [...datas]; // copying the old datas array
    newArr[index] = e.target.value; // replace e.target.value with whatever you want to change it to

    setDatas(newArr); // ??
}

return (
    
        { datas.map( (data, index) => {
              

                
              
          })
        }
    
)

Example 3: add object to array react hook

setTheArray([...theArray, newElement]);