How can I set the state and return JSX with the same function

user_15500393 0
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I am trying to create a function that when gets called, it sets the state to the object {item: 'whatever the user types', list: [...list, todo]}; However, I don't know how to set the new state and return <li>{todo}</li> at the same time. I have been stuck for a while so I'd appreciate if you can help me out.

const Todo = () => {
  const [state, setState] = useState({ item: '', list: [] });

  const setTodoValue = (e) => {
    setState((previousState) => {
      return { ...previousState, item: e.target.value };
    });
  };

  const addTodo = () => {
    setState((previousState) => {
      return {
        ...previousState,
        list: [...previousState.list, previousState.item],
      };
    });
  };

  return (
    <div>
      <input onChange={setTodoValue} type="text" />
      <button onClick={addTodo}> + </button>
      {}
    </div>
  );
};
use-state react-hooks reactjs html javascript
1 Answers

You can't, or won't, update state and simultaneously return JSX. You enqueue a state update, React updates the state, and you describe how to render the JSX from the state. The render return should take the state and map it to a bunch of list item li elements.

For more details on rendering JSX from arrays, see Lists and Keys.

Example rendering state.list into an unordered list:

const Todo = () => {
  const [state, setState] = useState({ item: '', list: [] });

  const setTodoValue = (e) => {
    setState((previousState) => {
      return { ...previousState, item: e.target.value };
    });
  };

  const addTodo = () => {
    setState((previousState) => {
      return {
        ...previousState,
        list: [...previousState.list, previousState.item],
      };
    });
  };

  return (
    <div>
      <input onChange={setTodoValue} type="text" />
      <button type="button" onClick={addTodo}> + </button>
      <ul>
        {state.list.map(todo => (
          <li key={todo}>{todo}</li>
        ))}
      </ul>
    </div>
  );
};
user_86908570
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