Updating an array nested in an array of object in React

In order to update the nested state, you need to map over the state and update the specific question id.

Here is the code for adding and removing choices.

let initialState = [
    {
        "question": 2,
        "choices": ["Heart Disease", "GERD", "ASTMA"]
    },
    {
        "question": 4,
        "choices": ["Heart Disease", "GERD", "ASTMA"]
    },
    {
        "question": 9,
        "choices": ["Heart Disease", "GERD", "ASTMA"]
    }
];

const [questions, setQuestions] = React.useState(initialState);

const addChoice = (questionId, choice) => {
    setQuestions(question.map(q => {
        if(q.question === questionId){
            return {...q, choices: [...q.choices, choice]}
        }
        return q;
    }))
};

const removeChoice = (questionId, choice) => {
    setQuestions(question.map(q => {
        if(q.question === questionId){
            return {...q, choices: q.choices.filter(c => c !== choice)}
        }
        return q;
    }))
};

In case you meant that you need to change the choices based on the question number dynamically. Then maybe below should do the job. It is written on the fly and not tested.

const [questions, setQuestions] = React.useState(defaultObject);

function questionSelected(questionNumber) {
    const temp = questions;
    const question = temp.find(n => n.question == questionNumber);
    question.choices = ['New', 'Choices'];
    setQuestions([...temp]);
}

Hope it helps.