In React, updating the state of a component is a common task. One way to update an object in the state is to create a new object with the updated properties and set it as the new state. However, simply setting the state with the new object may not always trigger a re-render of the component, which can lead to unexpected behavior.

To ensure that the component is re-rendered with the updated state, we can force a re-render by using a technique called "object spreading". In this technique, we create a new object by copying the properties of the original object and adding the updated properties to it. This new object is then set as the new state.

Let's take a look at an example of how to update an object in the state and force a re-render in React:

import React, { useState } from 'react';

function App() {
  const [questions, setQuestions] = useState({
    1: { question: 'What is React?', answer: 'React is a JavaScript library for building user interfaces.' },
    2: { question: 'What is useState?', answer: 'useState is a hook that allows you to add state to a functional component.' }
  });

  const handleUpdateAnswer = (questionId, newAnswer) => {
    const updatedQuestion = {
      ...questions[questionId],
      answer: newAnswer
    };

    setQuestions({
      ...questions,
      [questionId]: updatedQuestion
    });
  };

  return (
    <div>
      {Object.keys(questions).map((questionId) => (
        <div key={questionId}>
          <h3>{questions[questionId].question}</h3>
          <p>{questions[questionId].answer}</p>
          <button onClick={() => handleUpdateAnswer(questionId, 'This is the updated answer.')}>Update answer</button>
        </div>
      ))}
    </div>
  );
}

export default App;

### Example

Force rerender modified object.

    questions.name="demo"
    setQuestions({...questions});

In this example, we have an object called questions in the state, which contains two questions with their corresponding answers. We also have a function called handleUpdateAnswer, which updates the answer of a question based on the question ID.

When handleUpdateAnswer is called, we create a new object called updatedQuestion by copying the properties of the original question using the object spreading technique, and updating the answer property with the new answer.

We then update the state of the component by creating a new object called updatedQuestions using the object spreading technique again, and setting the updated question object as the value for the specified question ID.

This method of updating the state with a new object ensures that the component is re-rendered with the updated state, because React detects that the state has changed and triggers a re-render of the component.

In conclusion, updating a JavaScript object in the state and forcing a re-render in React can be achieved by using the object spreading technique to create a new object with the updated properties, and setting it as the new state. This ensures that the component is re-rendered with the updated state and avoids unexpected behavior.