Bootstrap snippet. calculator

HTML code

Copy, paste, change, customize and run the following HTML code to get a result like the one shown in the preview selection

İŞTE KOD 

<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <title>JavaScript Projects</title>
    <meta ID="description" content="">
    <meta ID="viewport" content="width=device-width, initial-scale=1">
    <!-- Latest compiled and minified CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" crossorigin="anonymous">
    <style>
        #output {
            height: 45px;
            background-color: black;
            color: aqua;
            width: 100%;
            font-size: 2em;
            padding: 5px;
            text-align: right;
            margin-bottom: 25px;
            overflow: hidden;
        }
             #mycalcu {
            width: 350px;
            background-color: dimgray;
            height: 350px;
            padding: 5px;
        }
          .cbutton {
            font-size: 2em;
            width: 40px;
            margin: 4px;
            padding: 4px;
        }
        .container {
            padding: 25px;
        }
    </style>
</head>
<body>
    <div class="container">
        <div id="mycalcu">
            <div class="col-xs-12">
                <div id="output"></div>
                <div class="col-xs-12">
                    <div class="btn btn-primary cbutton">1</div>
                    <div class="btn btn-primary cbutton">2</div>
                    <div class="btn btn-primary cbutton">3</div>
                    <div class="btn btn-primary cbutton">+</div>
                    <div class="btn btn-primary cbutton">C</div>
                </div>
                <div class="col-xs-12">
                    <div class="btn btn-primary cbutton">4</div>
                    <div class="btn btn-primary cbutton">5</div>
                    <div class="btn btn-primary cbutton">6</div>
                    <div class="btn btn-primary cbutton">-</div>
                </div>
                <div class="col-xs-12">
                    <div class="btn btn-primary cbutton">7</div>
                    <div class="btn btn-primary cbutton">8</div>
                    <div class="btn btn-primary cbutton">9</div>
                    <div class="btn btn-primary cbutton">*</div>
                </div>
                <div class="col-xs-12">
                    <div class="btn btn-primary cbutton">.</div>
                    <div class="btn btn-primary cbutton">0</div>
                    <div class="btn btn-primary cbutton">=</div>
                    <div class="btn btn-primary cbutton">/</div>
                </div>
            </div>
        </div>
    </div>
    <script>
        var mybtn = document.getElementsByClassName("cbutton");
        var myOutput = document.getElementById("output");
        var myCal = '';
        var myCom = false;
        var mySwitch = false;
        var myOpe = ["+", "-", "*", "/"];
        //console.log(mybtn);
        for (var i = 0; i < mybtn.length; i++) {
            mybtn[i].addEventListener("click", function () {
                var myValue = this.innerHTML;
                if (myCom || myCal == "0") {
                    myCom = false;
                    myCal = '';
                }
                if (myValue == "+" || myValue == "-" || myValue == "*" || myValue == "/") {
                    if (mySwitch) {
                        mySwitch = false;
                        if (myOpe.indexOf(myOutput.innerHTML.slice(-1)) > -1) {
                            myCal = myCal.substring(0, myCal.length - 1);
                        } else {
                            myCal = eval(myCal);
                        }
                    }
                    mySwitch = true;
                }
                if (myValue == "=") {
                    myValue = '';
                    if (myOpe.indexOf(myOutput.innerHTML.slice(-1)) == -1) {
                        myCal = eval(myCal);
                    }
                } else if (myValue == "C") {
                    myCal = 0;
                    myCom = true;
                } else if (myOutput.innerHTML.indexOf(".") > -1 && myValue == ".") {
                    myValue = '';
                } else {
                    myCal = myCal + myValue;
                }
                myOutput.innerHTML = myCal;
            });
        }
    </script>
</body>
</html>