サンプルコードで身につける: オブジェクトの型

const book: { title: string; pages: number } = {
  title: "TypeScript入門",
  pages: 320,
};

console.log(book.title);
console.log(book.pages);

// book.pages = "たくさん"; // number に string は入れられずエラー
console.log(book.title + "は" + book.pages + "ページです");

const weatherReport: {
  city: string;
  temperature: { morning: number; noon: number };
} = {
  city: "Tokyo",
  temperature: { morning: 18, noon: 26 },
};

console.log(weatherReport.city);
console.log(weatherReport.temperature.morning);
console.log("昼までに" + (weatherReport.temperature.noon - weatherReport.temperature.morning) + "度上昇");

function calcTotal(item: { unitPrice: number; quantity: number }): number {
  return item.unitPrice * item.quantity;
}

console.log(calcTotal({ unitPrice: 480, quantity: 3 }));
console.log(calcTotal({ unitPrice: 1200, quantity: 2 }));

// calcTotal({ unitPrice: 480 }); // quantity が足りないのでエラー

function analyzeScores(scoreList: number[]): { max: number; min: number; average: number } {
  let maxValue = scoreList[0];
  let minValue = scoreList[0];
  let sum = 0;
  for (const score of scoreList) {
    if (score > maxValue) maxValue = score;
    if (score < minValue) minValue = score;
    sum += score;
  }
  return { max: maxValue, min: minValue, average: sum / scoreList.length };
}

const summary = analyzeScores([80, 92, 67, 75]);
console.log(summary.max);
console.log(summary.min);
console.log(summary.average);

const members: { id: number; userName: string; age: number }[] = [
  { id: 1, userName: "Taro", age: 28 },
  { id: 2, userName: "Hanako", age: 25 },
  { id: 3, userName: "Jiro", age: 31 },
];

const lines = members.map(function (member) {
  return member.id + ": " + member.userName + "(" + member.age + "歳)";
});

for (const line of lines) {
  console.log(line);
}