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學習FP的JavaScript基礎

你有一個學生陣列，每位學生都有名字與成績，我們要完成以下幾個任務：

const students = [
  { name: "小美", score: 85 },
  { name: "阿良", score: 42 },
  { name: "小凱", score: 77 },
  { name: "阿珍", score: 59 },
  { name: "小安", score: 91 },
];

任務一：用 map 產生「評語」陣列（陣列方法 + 純函數）​

把每位學生都轉換成一句評語：小美的成績是85分，表現不錯喔！

// 請寫出純函數 `getComment(student)`，回傳評語字串
// 然後用 map 建立新陣列 `comments`
const comments = students.map(function ({ name, score }) {
  return `${name}的成績是${score}分，表現不錯喔！`;
});
["小美的成績是85分，表現不錯喔！","阿良的成績是42分，表現不錯喔！","小凱的成績是77分，表現不錯喔！","阿珍的成績是59分，表現不錯喔！","小安的成績是91分，表現不錯喔！"]

任務二：用 filter 過濾不及格的學生​

找出所有成績低於 60 分的學生（使用純函數）

// 請寫出純函數 `isFailed(student)`，回傳 true / false
// 然後用 filter 建立新陣列 `failedStudents`
function isFailed(student) {
  return student.score < 60;
}
let failedStudents = students.filter(isFailed);
[// [object Object]
{
  "name": "阿良",
  "score": 42
},// [object Object]
{
  "name": "阿珍",
  "score": 59
}]

任務三：用 reduce 計算全班平均成績​

// 請用 reduce 算出總分，再除以學生數量，算出平均分數 averageScore
const averageScore = students.reduce((sum, student) => {
  return sum + student.score;
}, 0);
//354

任務四：製作一個高階函數 makeScoreFilter(minScore)​

它會回傳一個函數，幫你篩選成績大於某數字的學生，例如：

// const filterAbove70 = makeScoreFilter(70);
// const goodStudents = students.filter(filterAbove70);
function makeScoreFilter(minScore) {
  return students.filter((student) => student.score > minScore);
}
makeScoreFilter(85);
[// [object Object
{
  "name": "小安",
  "score": 91
}]

額外挑戰（選擇做）​

製作一個純函數 toGrade(score)，可以將數字轉為等級

然後幫每位學生加上 grade 欄位，變成這樣：

// { name: '小美', score: 85, grade: 'B' }

function toGrade(score) {
  if (score >= 90) return "A";
  if (score >= 80) return "B";
  if (score >= 70) return "C";
  if (score >= 60) return "D";
  return "F";
}

const studentsWithGrades = students.map((student) => {
  return {
    ...student,
    grade: toGrade(student.score),
  };
});
console.log(studentsWithGrades);
[
  // [object Object]
  {
    name: "小美",
    score: 85,
    grade: "B",
  }, // [object Object]
  {
    name: "阿良",
    score: 42,
    grade: "F",
  }, // [object Object]
  {
    name: "小凱",
    score: 77,
    grade: "C",
  }, // [object Object]
  {
    name: "阿珍",
    score: 59,
    grade: "F",
  }, // [object Object]
  {
    name: "小安",
    score: 91,
    grade: "A",
  },
];