[JavaScript] 연산

깨구르르 2024. 3. 7. 18:30

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사칙연산

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        //사칙연산
        let result = 0;
        result = 10 + 20;
        document.write(result + "<br>");
        result = 10 - 20;
        document.write(result + "<br>");
        result = 10 * 20;
        document.write(result + "<br>");
        result = 10 / 20;
        document.write(result + "<br>");
        result = 10 % 3;
        document.write(result + "<br>");
    </script>
</head>
<body>
    
</body>
</html>

증감연산

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        //증감연산
        let val = 10;
        document.write(++val + "<br>"); //전위증감
        document.write(val++ + "<br>"); //후위증감
        document.write(val + "<br>");
    </script>
</head>
<body>
    
</body>
</html>

비교연산

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        //비교연산
        let val1 = 20;
        document.write((val > val1) + "<br>");     //false

        //비교연산
        let isResult = 10 == 10;
        document.write(isResult + "<br>");  //true
        isResult = 10 == '10';
        document.write(isResult + "<br>");  //true (자동형변환 후 값을 비교해서)
        isResult = 10 === '10';
        document.write(isResult + "<br>");  //false (자료형이 일치하는지도 비교함)

        //비교연산(C언의의 영향) => 안정성이 떨어짐
        isResult = false == '0';
        document.write(isResult + "<br>");  //true (false를 0과 같은 개념으로 봐서)
        isResult = false == 0;
        document.write(isResult + "<br>");  //true
        isResult = "" == [];
        document.write(isResult + "<br>");  //true
        isResult = 0 == [];
        document.write(isResult + "<br>");  //true
    </script>
</head>
<body>
    
</body>
</html>

논리연산

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        //논리연산
        document.write((true && true) + "<br>");  //true
        document.write((false && true) + "<br>"); //false
        document.write((true || false) + "<br>"); //true
        document.write(!false + "<br>");        //true
    </script>
</head>
<body>
    
</body>
</html>

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