2018. 10. 15. 01:59 javascript

javascript 조건문(conditional statement)

제어문

해당 언어를 보다 효율적으로 사용할 수 있도록 하는 문장

- 조건문, 반복문


조건문

 


if

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<!DOCTYPE html>
<html lang="ko">
    <head>
        <meta charset="utf-8">
        <title>조건문 if</title>
        <script>
            var a = 10;
            if (a > 5) {
                document.write("10 > 5");
            }
        </script>
    </head>
    <body>      
    </body>
</html>
cs


if - else

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<!DOCTYPE html>
<html lang="ko">
    <head>
        <meta charset="utf-8">
        <title>조건문 if-else</title>
        <script>
            var a = 1;
            if (a > 5) {
                document.write(a + " > 5");
            }           
            else {
                document.write(a + " < 5");                
            }
        </script>
    </head>
    <body>      
    </body>
</html>
cs


if - else if - else

 
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<!DOCTYPE html>
<html lang="ko">
    <head>
        <meta charset="utf-8">
        <title>조건문 if-else if-else</title>
        <script>
            var a = 2;
            if (a < 5) {
                document.write(a + " < 5");
            }           
            else if (a > 3) {
                document.write(a + " > 3");                
            }
            else if (a == 2) { 
                // 위에 (a < 5) 기준을 먼저 만족하여 이 구문은 실행안됨.
                document.write(a);                
            }
            else {
                document.write(a);                
            }
        </script>
    </head>
    <body>      
    </body>
</html>
cs


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<!DOCTYPE html>
<html lang="ko">
    <head>
        <meta charset="utf-8">
        <title>숫자 맞추기</title>
        <script>
            var computerNumber = 4;        // 정답
            var nGuesses = 0;                // 추측 횟수
 
            function guess() {
                var result = "";        // 결과 메시지
 
                // 사용자가 입력한 값을 받아서 변수 number에 대입한다. 
                var number = parseInt(document.getElementById("user").value);
                nGuesses++;                    // 추측 횟수를 증가시킨다. 
 
                if (number == computerNumber) result = "성공입니다.";
                else if (number < computerNumber) result = "낮습니다.";
                else result = "높습니다.";
 
                document.getElementById("result").value = result;
                document.getElementById("guesses").value = nGuesses;
                return true;
            }
        </script>
    </head>
    <body>     
         숫자를 맞추세요.<br>(숫자는 1부터 10 사이에 있습니다.)<br><br>
        <form>
            <label for="user">숫자 : </label>
            <input type="text" id="user" size="5">
            <input type="button" value="확인" onclick="guess();"><br>
            <label for="guesses">추측횟수 : </label>
            <input type="text" id="guesses" size="5"><br>
            <label for="result">힌트 : </label>
            <input type="text" id="result" size="16">
        </form>  
    </body>
</html>
cs


switch

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<!DOCTYPE html>
<html lang="ko">
    <head>
        <meta charset="utf-8">
        <title>switch</title>
        <script>
            var a = 3;
            switch (a) {
                case 2 : alert("a=2");
                    break;
                case 3 : alert("a=3");  
                    break;
                case 4 : alert("a=4");
                    break;
                default : alert(a)
            }
        </script>
    </head>
    <body>      
    </body>
</html>
cs








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