Open Closed Principle

If we want to add a new type in questions, we need to update the switch case statement in printQuiz function. This violates Open Closed Principle.

function printQuiz(questions) {
  questions.forEach((question) => {
    console.log(question.description);
    switch (question.type) {
      case "boolean":
        console.log("1. True");
        console.log("2. False");
        break;
      case "multipleChoice":
        question.options.forEach((option, index) => {
          console.log(index + 1, option);
        });
        break;
      case "text":
        console.log("Answer: _____");
        break;
    }
    console.log("");
  });
}

const questions = [
  {
    type: "boolean",
    description: "This notes are useful",
  },
  {
    type: "multipleChoice",
    description: "Favorite fruit?",
    options: ["Apple", "Orange", "Pineapple", "Grape"],
  },
  {
    type: "text",
    description: "What is your job?",
  },
];

printQuiz(questions);

// This notes are useful
// 1. True
// 2. False

// Favorite fruit?
// 1 Apple
// 2 Orange
// 3 Pineapple
// 4 Grape

// What is your job?
// Answer: _____

{
  type: "range",
  description: "What is the speed limit?"
}

case 'range':
  console.log("Minimum: _____")
  console.log("Maximum: _____")
  break;

Open Closed means our utility functions to be Open for extension, but closed for modification.

If we change the code outside the function, ideally that should not result in the code change inside function.

class BooleanQuestion {
  constructor(description) {
    this.description = description;
  }

  printQuestionChoices() {
    console.log("1. True");
    console.log("2. False");
  }
}

class MultipleChoiceQuestion {
  constructor(description, options) {
    this.description = description;
    this.options = options;
  }

  printQuestionChoices() {
    this.options.forEach((option, index) => {
      console.log(index + 1, option);
    });
  }
}

class TextQuestion {
  constructor(description) {
    this.description = description;
  }

  printQuestionChoices() {
    console.log("Answer: _____");
  }
}

class RangeQuestion {
  constructor(description) {
    this.description = description;
  }

  printQuestionChoices() {
    console.log("Minimum: _____");
    console.log("Maximum: _____");
  }
}

function printQuiz(questions) {
  questions.forEach((question) => {
    console.log(question.description);
    question.printQuestionChoices();
    console.log("");
  });
}

const questions = [
  new BooleanQuestion("This notes are useful"),
  new MultipleChoiceQuestion("Favorite fruit?", [
    "Apple",
    "Orange",
    "Pineapple",
    "Grape",
  ]),
  new TextQuestion("What is your job?"),
  new RangeQuestion("What is the speed limit?"),
];

printQuiz(questions);

// This notes are useful
// 1. True
// 2. False

// Favorite fruit?
// 1 Apple
// 2 Orange
// 3 Pineapple
// 4 Grape

// What is your job?
// Answer: _____

// What is the speed limit?
// Minimum: _____
// Maximum: _____