자바스크립트 Tutorial By Ellie (7)

'use strict';

// 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();
    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);
    console.log(result);
    console.log(array); 
  }
  
  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((student) => student.score === 80);
      console.log(result);
    }
  
  // Q6. make an array of enrolled students
  {
    const result = students.filter((student) => student.enrolled === false);
    console.log(result);
  }
  

  // Q7. make an array containing only the students' scores
  // result should be: [45, 80, 90, 66, 88]
  {   // callback함수는 이해하기 쉽게 (student)
      const result = students.map((student) => student.score * 2);
      console.log(result);
  }
  
  // Q8. check if there is a student with the score lower than 50
  {
    console.clear();
    const result = students.some((student) => student.score < 50);
    console.log(result);

    const result2 = !students.every((student) => student.score >= 50);
    console.log(result2);
  }
  
  // Q9. compute students' average score
  {
      const result = students.reduce((prev, curr) => 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)
        .filter((score) => score >= 50)
        .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);   
  }