How to check if an object has a key?-CodePudding

I have a questionnaire which shows questions in prompt. Each subsequent question depends on the user's answer. Now each question has two answers and a question ID to show next. And the code shows the question depending on the answer. But not every question will have two possible answers. How can I show answer options in prompt depending on the presence of answer_2. For example, if there is answer_2, then:

const answer = prompt(`${question}`, `${answer_1.text} / ${answer_2.text}`)

If answer_2 is missing then:

const answer = prompt(`${question}`, `${answer_1.text}`)

Here my code:

const questions = [{
    id: "1",
    question: "q1",
    answer_1: {
      text: "a1",
      next_question: "2",
    },
    answer_2: {
      text: "a2",
      next_question: "3",
    },
  },
  {
    id: "2",
    question: "q2",
    answer_1: {
      text: "a1",
      next_question: "",
    },
  },
  {
    id: "3",
    question: "q3",
    answer_1: {
      text: "a1",
      next_question: "",
    },
    answer_2: {
      text: "a2",
      next_question: "4",
    },
  },
  {
    id: "4",
    question: "q4",
    answer_1: {
      text: "a1",
      next_question: "",
    },
  },
];

//=== question display

function quiz({
  question,
  answer_1,
  answer_2
}) {
  const answer = prompt(`${question}`, `${answer_1.text} / ${answer_2.text}`);
  let nextQuestion;
  if (answer == answer_1.text) {
    nextQuestion = answer_1.next_question;
  } else if (answer == answer_2.text) {
    nextQuestion = answer_2.next_question;
  } else {
    alert("Invalid answer");
  }

  if (nextQuestion) {
    quiz(questions.find((q) => q.id == nextQuestion));
  }
}

quiz(questions[0]);

CodePudding user response：

For questions with no answer_2, you get undefined as value for answer_2 in quiz function. With that you can use an if (answer_2) statement and output what you want, like so:

const questions = [
  {
    id: "1",
    question: "q1",
    answer_1: {
      text: "a1",
      next_question: "2"
    },
    answer_2: {
      text: "a2",
      next_question: "3"
    }
  },
  {
    id: "2",
    question: "q2",
    answer_1: {
      text: "a1",
      next_question: ""
    }
  },
  {
    id: "3",
    question: "q3",
    answer_1: {
      text: "a1",
      next_question: ""
    },
    answer_2: {
      text: "a2",
      next_question: "4"
    }
  },
  {
    id: "4",
    question: "q4",
    answer_1: {
      text: "a1",
      next_question: ""
    }
  }
];

//=== question display

function quiz({ question, answer_1, answer_2 }) {
  let answer;
  if (answer_2) {
    answer = prompt(`${question}`, `${answer_1.text} / ${answer_2.text}`);
  } else {
    answer = prompt(`${question}`, `${answer_1.text}`);
  }
  let nextQuestion;
  if (answer == answer_1.text) {
    nextQuestion = answer_1.next_question;
  } else if (answer_2 && answer == answer_2.text) {
    nextQuestion = answer_2.next_question;
  } else {
    alert("Invalid answer");
  }

  if (nextQuestion) {
    quiz(questions.find((q) => q.id == nextQuestion));
  }
}

quiz(questions[0]);

CodePudding user response：

Since a number divided by one is that same number, 1 can be considered your default value.

const a1 = answer_1.text;
const a2 = answer_2?.text || 1;