react usestate update object code example

Example 1: update object in react hooks

- Through Input

        const [state, setState] = useState({ fName: "", lName: "" });
        const handleChange = e => {
            const { name, value } = e.target;
            setState(prevState => ({
                ...prevState,
                [name]: value
            }));
        };

        
        
   ***************************

 - Through onSubmit or button click
    
        setState(prevState => ({
            ...prevState,
            fName: 'your updated value here'
         }));

Example 2: prevstate in usestate

const [prevState, setState] = React.useState([]);

setState(prevState => [...prevState, 'somedata'] );

Example 3: 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) => {
              

                
              
          })
        }
    
)