20 minutes arithmetic calculator

gistfile1.txt

<script type="text/javascript" src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<style type="text/css">
    body {
        background: #c3c3c3;
    }
    
    .body .buttons {
        float: left;
        width: 20%;
        height: 50px;
        text-align: center;
        padding-top: 20px;
        font-size: 25px;
        cursor: pointer;
    }

    .result {
        height: 50px;
        background: #efefef;
        padding: 10px;
    }

    .calculator {
        height: 270px;
        background: white;
        width: 400px;
        margin-left: auto;
        margin-right:auto;;
    }

</style>
<script type="text/javascript">
    var calculator = new function() {
        this.current = 0;
        this.previous = 0;
        this.currentOperator = null;
        this.calculated = false;

        this.sum = function() {
            this.currentOperator = '+';
            this.previous = this.current;
            this.reset();
        };

        this.reset = function() {
            $('.result').html('');
            this.calculated = false;
        };

        this.substract = function() {
            this.currentOperator = '-';
            this.previous = this.current;
            this.reset();
        };

        this.multiply = function() {
            this.currentOperator = 'X';
            this.previous = this.current;
            this.reset();
        };

        this.divide = function() {
            this.currentOperator = '/';
            this.previous = this.current;
            this.reset();
        };

        this.numClick = function(value) {
            if(this.calculated == true)
                this.reset();

            $('.result').html(this.current = Number($('.result').html() + value));
        };

        this.getResult = function() {
            this.calculated = true;

            if(this.currentOperator == '+')
                $('.result').html(this.current + this.previous);
            else if(this.currentOperator == '-')
                $('.result').html(this.previous - this.current);
            else if(this.currentOperator == 'X')
                $('.result').html(this.previous * this.current);
            else if(this.currentOperator == '/')
                $('.result').html(this.previous / this.current);
        };
    };
</script>
<div class="calculator">
    <div class="header">
        <div class="result"></div>
    </div>
    <div class="body">
        <div class="buttons num" onclick="calculator.numClick(1);">1</div>
        <div class="buttons num" onclick="calculator.numClick(2);">2</div>
        <div class="buttons num" onclick="calculator.numClick(3);">3</div>
        <div class="buttons num" onclick="calculator.numClick(4);">4</div>
        <div class="buttons num" onclick="calculator.numClick(5);">5</div>
        <div class="buttons num" onclick="calculator.numClick(6);">6</div>
        <div class="buttons num" onclick="calculator.numClick(7);">7</div>
        <div class="buttons num" onclick="calculator.numClick(8);">8</div>
        <div class="buttons num" onclick="calculator.numClick(9);">9</div>
        <div class="buttons num" onclick="calculator.numClick(0);">0</div>
        <div class="buttons operator" onclick="calculator.sum();">+</div>
        <div class="buttons operator" onclick="calculator.substract();">-</div>
        <div class="buttons operator" onclick="calculator.multiply();">X</div>
        <div class="buttons operator" onclick="calculator.divide();">/</div>
        <div class="buttons operator" onclick="calculator.getResult();">=</div>
    </div>
</div>