arrayQuiz-answer.js

console.clear();
// Q1. make a string out of an array
{
 const fruits = ['apple', 'banana', 'orange'];
 const result = fruits.join();
 console.log(result);
}

// Q2. make an array out of a string
{
 const fruits = '🍎, 🥝, 🍌, 🍒';
 const result = fruits.split(',');
 console.log(result);
}

// Q3. make this array look like this: [5, 4, 3, 2, 1]
{
 const array = [1, 2, 3, 4, 5];
 const result = array.reverse(); // 배열 자체를 reverse함(array도)
 console.log(result);
 console.log(array);
}

// Q4. make new array without the first two elements
{
 const array = [1, 2, 3, 4, 5];
 const result = array.slice(2, 5); // splice -> 배열 자체를 수정, slice는 end 값은 배제됨으로 4가 아닌 5로 설정해야 함
}

class Student {
 constructor(name, age, enrolled, score) {
 this.name = name;
 this.age = age;
 this.enrolled = enrolled;
 this.score = score;
 }
}
const students = [
 new Student('A', 29, true, 45),
 new Student('B', 28, false, 80),
 new Student('C', 30, true, 90),
 new Student('D', 40, false, 66),
 new Student('E', 18, true, 88),
];

// Q5. find a student with the score 90
{
 const result = students.find(function(student) {
 // console.log(student);
 return student.score === 90; // true or false로 리턴
 });
 console.log(result);
}

// Q6. make an array of enrolled students(수업에 등록한 학생만!)
{
 const result = students.filter((student) => student.enrolled);
 console.log(result);
}

// Q7. make an array containing only the students' scores
// result should be: [45, 80, 90, 66, 88]
{
 const result = students.map((student) => student.score);
 console.log(result)
}

// Q8. check if there is a student with the score lower than 50
{
 const result = students.some((student) => student.score < 50);
 console.log(result);

 const result1 = students.every((student) => student.score < 50); // 모든 배열이 조건을 만족할 때만 true가 나옴; 모든 학생들이 50점 미만일 때만 true
 console.log(result1);
}

// Q9. compute students' average score
{
 const result = students.reduce((prev, curr) => { // reduceRight; 뒤에서부터 시작
 console.log('------');
 console.log(prev);
 console.log(curr);
 return prev + curr.score;
 }, 0);
 console.log(result / students.length);
}

// Q10. make a string containing all the scores
// result should be: '45, 80, 90, 66, 88'
{
 const result = students
 .map((student) => student.score)
 .join();
 console.log(result);
}

// Bonus! do Q10 sorted in ascending order
// result should be: '45, 66, 80, 88, 90'
{
 const result = students
 .map((student) => student.score)
 .sort((a, b) => a - b)
 .join()
 console.log(result);
}