<h1>Javascript Basit Hesap Makinesi</h1>
    
    <label>Küçük sayı : </label>
    <input type="number" id="sayi1">

    <select id="islem">
        <option value="topla">+</option>
        <option value="cikar">-</option>
        <option value="carp">*</option>
        <option value="bol">/</option>
    </select>

    <label>Büyük sayı : </label>
    <input type="number" id="sayi2">

    <button id="buton">Sonucu Bul</button>

    <div id="sonuc"></div>
    
    <script>
        var sonuc;
        function hesapla(){
            var sayi1=document.getElementById("sayi1").value;
            var sayi2=document.getElementById("sayi2").value;
            var islem=document.getElementById("islem").value;
    
            var s1 = Number(sayi1);
            var s2 = Number(sayi2);

            if(islem == 'topla')
                sonuc = s1 + s2;
            else if(islem == 'cikar')
                sonuc = s1 - s2;
            else if(islem == 'carp')
                sonuc = s1 * s2;
            else
                sonuc = s1 / s2;

            document.getElementById("sonuc").innerHTML = "Sonuc : " + sonuc;
        }

        var hesaplaBtn=document.getElementById("buton");
        hesaplaBtn.onclick=hesapla;

    </script>