[FrontEnd2] JS 연습문제 풀이 (switch, while ,for 문)

    SMALL

    1. Switch

    (1) 1,2,3 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var num = prompt("정수를 입력하세요")
        num = parseInt(num)

        switch(num) {
            case 1:
                document.write("one", "<br>")
                break;
            case 2:
                document.write("two", "<br>")
                break;
            case 3:
                document.write("three", "<br>")
                break;
            default:
                document.write("I don't know", "<br>")
                break;
        }
    </script>
</head>
<body>
    
</body>
</html>

     

     

    (2) 조건에 따른 지하철 요금 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var person = prompt("성인, 미성년자, 노인 중 하나를 입력하세요")

        switch(person){
            case "성인":
                document.write("1100원", "<br>")
                break;
            case "미성년자":
                document.write("900원", "<br>")
                break;
            case "노인":
                document.write("무료", "<br>")
                break;   
        }
    </script>
</head>
<body>
    
</body>
</html>

     

     

    (3) 성적에 따른 학점 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var score = prompt("시험 점수를 입력하세요")

        switch(true){ // 범위 사용시 변수 자리에는 true 넣어줌.
            case (score<100 && score >= 90):
                document.write("A학점", "<br>")
                break;
            case (score<90 && score >= 80):
                document.write("B학점", "<br>")
                break;
            case (score<80 && score >= 70):
                document.write("C학점", "<br>")
                break;
        }
    </script>
</head>
<body>
    
</body>
</html>

     

     

    (4) 알파벳에 따른 단어 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var char = prompt("알파벳을 입력하세요.")

        switch(char){
            case "A": case "a":
                document.write("Apple", "<br>")
                break;
            case "B": case "b":
                document.write("Baby", "<br>")
                break;
            case "C": case "c":
                document.write("Chrome", "<br>")
                break;
        }
    </script>
</head>
<body>
    
</body>
</html>

     

     

    (5) 사칙연산

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var num1 = prompt("첫 번째 정수를 입력하세요.")
        num1 = parseInt(num1)

        var num2 = prompt("두 번째 정수를 입력하세요.")
        num2 = parseInt(num2)

        var symbol = prompt("연산자를 입력하세요.")

        switch (symbol) {
            case "+": 
                document.write(num1 + "+" + num2 + "=" + (num1+num2), "<br>")
                break;
            case "-": 
                document.write(num1 + "-" + num2 + "=" + (num1-num2), "<br>")
                break;
            case "*": 
                document.write(num1 + "x" + num2 + "=" + (num1*num2), "<br>")
                break;
            case "/": 
                document.write(num1 + "/" + num2 + "=" + (num1/num2), "<br>")
                break;
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    1. While

    (1) 입력 숫자만큼 문장 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var num = prompt("횟수를 입력하세요.")
        num = parseInt(num)

        var i = 1;

        while (i<=num){
            document.write("JavaScript!", "<br>")
            i++
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (2) 입력 숫자의 구구단 구하기

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var dan = prompt("몇 단?")
        dan = parseInt(dan)

        var i = 1;

        while (i<=9){
            document.write(dan + "x" + i + "=" + (dan*i), "<br>")
            i++;
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (3) 시작 숫자와 끝 숫자 사이의 짝수 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var start = prompt("시작 숫자")
        start = parseInt(start)

        var end = prompt("끝 숫자")
        end = parseInt(end)

        while(start<=end){
            if(start%2==0){
                document.write(start + " ")
                start++
            }
            else{
                start++
            }
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (4) 시작 숫자와 끝 숫자 사이의 홀수 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var start = prompt("시작 숫자")
        start = parseInt(start)

        var end = prompt("끝 숫자")
        end = parseInt(end)

        while(start<=end){
            if(start%2==1){
                document.write(start + " ")
                start++
            }
            else{
                start++
            }
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (5) 시작 숫자부터 끝 숫자까지의 합 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var start = prompt("시작 숫자")
        start = parseInt(start)

        var end = prompt("끝 숫자")
        end = parseInt(end)

        var sum = 0;

        while(start<=end){
            sum += start
            start++
        }

        document.write("합: " + sum , "<br>")
    </script>
</head>
<body>
    
</body>
</html>

     

    1. For

    (1) 입력 횟수만큼 문장 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var num = prompt("횟수를 입력하세요.")
        num = parseInt(num)

        for (var i=1; i<=num; i++){
            document.write("HTML, CSS, JavaScript, JQuery", "<br>")
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (2) 입력 숫자의 구구단 구하기

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var dan = prompt("몇 단?")
        dan = parseInt(dan)

        for (var i = 1; i<=9 ; i++){
            document.write(dan + "x" + i + "=" + (dan*i), "<br>")
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (3) 시작 숫자와 끝 숫자 사이의 짝수 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var start = prompt("시작 숫자 입력")
        start = parseInt(start)

        var end = prompt("끝 숫자 입력")
        end = parseInt(end)

        for (var i = start; i<=end; i++) {
            if(start%2==0){
                document.write(start, " ")
                start++
            }
            else{
                start++
            }
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (4) 시작 숫자와 끝 숫자 사이의 홀수 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var start = prompt("시작 숫자 입력")
        start = parseInt(start)

        var end = prompt("끝 숫자 입력")
        end = parseInt(end)

        for (var i = start; i<=end; i++) {
            if(start%2==1){
                document.write(start, " ")
                start++
            }
            else{
                start++
            }
        }
    </script>
</head>
<body>
    
</body>
</html>

     

    (5) 시작 숫자부터 끝 숫자까지의 합 출력

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var start = prompt("시작 숫자 입력")
        start = parseInt(start)

        var end = prompt("끝 숫자 입력")
        end = parseInt(end)

        var sum = 0;

        for (var i = start; i<=end; i++) {
            sum += i          
        }
        
        document.write("합: " + sum, "<br>")
    </script>
</head>
<body>
    
</body>
</html>

     

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