取得平均年齡 - 現代 JavaScript 教學

撰寫函式 getAverageAge(users)，它會取得一個包含屬性 age 的物件陣列，並傳回平均年齡。

平均值的公式為 (age1 + age2 + ... + ageN) / N。

例如

          let john = { name: "John", age: 25 };
let pete = { name: "Pete", age: 30 };
let mary = { name: "Mary", age: 29 };

let arr = [ john, pete, mary ];

alert( getAverageAge(arr) ); // (25 + 30 + 29) / 3 = 28
        

function getAverageAge(users) {
  return users.reduce((prev, user) => prev + user.age, 0) / users.length;
}

let john = { name: "John", age: 25 };
let pete = { name: "Pete", age: 30 };
let mary = { name: "Mary", age: 29 };

let arr = [ john, pete, mary ];

alert( getAverageAge(arr) ); // 28