const [val, setVal]=useState("some");


const change=()=>{

setVal(5);

add();

}


const add=()=>{

console.log(val);

}




export default function App() {

  const [emp, setEmp] = useState({ name: "A", age: 5 });

  const update = () => {

    emp.age = 10;

    console.log()

    setEmp(emp);

  };

  return (

    <div className="App">

      <h1>Hello CodeSandbox</h1>

      <h2>{`${emp.name} : ${emp.age}`}</h2>

      <button onClick={update}>Update</button>

    </div>

  );

}


import { useState } from "react";
const App = () => {
  const [user, setUser] = useState({ firstName: "", lastName: "" });
  const updateUser = (first, last) => {
    setUser({ ...user, firstName: first });
    if (last) {
      updateLastName(last);
    }
  };
  const updateLastName = (last) => {
    setUser((us)=>{ ...user, lastName: last });
  };
  return (
    <>
      <div>
        First Name: {user.firstName}
        <br />
        Last Name: {user.lastName}
      </div>
      <button onClick={() => updateUser("Tom", "Cruise")}>Update User</button>
    </>
  );
};
export default App;


redux -> multiple slices update, combine reducer

where to use redux and where to use contextAPI


when to use keys in react







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