javascript_practice/계산기구현_if_else문활용.html at master · beaver84/javascript_practice · GitHub

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<!DOCTYPE html>
<html lang="ko">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <input type="text" id ="n1" /><br/>
    <input type="text" id ="op" /><br/>
    <input type="text" id ="n2" /><br/>
    <input type="button" onclick="calc()" value="계산"></button><br/>
    <div id="output"></div>


    <script>
        function calc(){
            var str1 = document.getElementById('n1').value;
            var str2 = document.getElementById('n2').value;
            var op = document.getElementById('op').value;
            var n1 = Number(str1);
            var n2 = Number(str2);

            var out = document.getElementById('output');
            var str = "";
            if ( op === "+"){
                str += "더하기: " + (n1 + n2) + "<br>";
            }else if (op === "-"){
                str += "빼기: " + (n1 - n2) + "<br>";
            }else if (op === "*"){
                str += "곱하기: " + (n1 * n2) + "<br>";
            }else if (op === "/"){
                str += "나누기: " + (n1 / n2) + "<br>";
            }else{
                str += "연산자에는 4칙연산자만 입력해 주세요.";
            }
            out.innerHTML = str;
        }

    </script>
</body>
</html>